SOLID Object-Oriented Design

This talk explains the object-oriented design principles that underly the SOLID acronym. It defines the principles in plain language and shows practical examples of their use by walking a simple bit of Ruby code through a series of refactorings that move it from specific and concrete to general and abstract.

Transcript

1. Sandi Metz
   @sandimetz Feb 2013
   SOLID
   Thursday, February 28, 13
   

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2. @sandimetz Feb 2013
   Your application will
   change.
   Thursday, February 28, 13
   

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3. @sandimetz Feb 2013
   Your application will
   change.
   How will that work out?
   Thursday, February 28, 13
   

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4. @sandimetz Feb 2013
   Thursday, February 28, 13
   

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5. @sandimetz Feb 2013
   Rigid
   Every change
   forces a cascade
   of related changes.
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6. @sandimetz Feb 2013
   Rigid
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7. @sandimetz Feb 2013
   Thursday, February 28, 13
   

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8. @sandimetz Feb 2013
   Fragile
   Each change
   breaks distant and
   apparently unrelated
   things.
   Thursday, February 28, 13
   

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9. @sandimetz Feb 2013
   Fragile
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10. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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11. @sandimetz Feb 2013
    Immobile
    The code is
    hopelessly entangled;
    reuse is impossible.
    Thursday, February 28, 13
    

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12. @sandimetz Feb 2013
    Immobile
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13. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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14. @sandimetz Feb 2013
    Viscous
    Behaving badly
    is the most attractive
    alternative.
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15. @sandimetz Feb 2013
    Viscous
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16. @sandimetz Feb 2013
    It didn’t start that way.
    Thursday, February 28, 13
    

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17. @sandimetz Feb 2013
    In the
    beginning,
    your
    application
    was
    perfect.
    Thursday, February 28, 13
    

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18. @sandimetz Feb 2013
    And then
    it changed.
    Thursday, February 28, 13
    

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19. @sandimetz Feb 2013
    Dependencies are
    killing you.
    Thursday, February 28, 13
    

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20. @sandimetz Feb 2013
    Dependencies are
    killing you.
    Design can save you.
    Thursday, February 28, 13
    

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21. @sandimetz Feb 2013
    http://www.martinfowler.com/bliki/DesignStaminaHypothesis.html
    Design Stamina Hypothesis
    Thursday, February 28, 13
    

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22. @sandimetz Feb 2013
    If your project succeeds,
    it will continue
    to cost you money.
    $$$
    Thursday, February 28, 13
    

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23. @sandimetz Feb 2013
    Design Principles and
    Design Patterns
    Robert Martin
    http://www.objectmentor.com
    Thursday, February 28, 13
    

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24. @sandimetz Feb 2013
    Single Responsibility
    Open/Closed
    Liskov Substitution
    Interface Segregation
    Dependency Inversion
    Principles
    Thursday, February 28, 13
    

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25. @sandimetz Feb 2013
    Single Responsibility
    A class should serve
    a single purpose.
    Thursday, February 28, 13
    

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26. @sandimetz Feb 2013
    Open/Closed
    A module should be
    open for extension
    but closed for modi cation.
    Thursday, February 28, 13
    

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27. @sandimetz Feb 2013
    Liskov Substitution
    Subclasses should be
    substitutable
    for their base classes.
    Thursday, February 28, 13
    

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28. @sandimetz Feb 2013
    Liskov Substitution
    Subclasses should be
    substitutable
    for their base classes.
    Let q(x) be a property provable about objects x of type T.
    Then q(y) should be true for objects y of type S where
    S is a subtype of T.
    Thursday, February 28, 13
    

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29. @sandimetz Feb 2013
    Interface Segregation
    Many client speci c interfaces
    are better than
    one general purpose interface.
    Thursday, February 28, 13
    

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30. @sandimetz Feb 2013
    Dependency Inversion
    Depend upon abstractions,
    do not depend upon
    concretions.
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31. @sandimetz Feb 2013
    Design is all about
    dependencies.
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32. @sandimetz Feb 2013
    When you know something
    you depend on it.
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33. @sandimetz Feb 2013
    If it changes
    you might change.
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34. @sandimetz Feb 2013
    Changeable Apps
    Loosely Coupled
    Highly Cohesive
    Easily Composable
    Context Independent
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35. @sandimetz Feb 2013
    Achieving Independence
    Single Responsibility
    Dependency Inversion
    Open/Closed
    Liskov Substitution
    Interface Segregation
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36. @sandimetz Feb 2013
    Example App
    Thursday, February 28, 13
    

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37. @sandimetz Feb 2013
    Get a CSV le from an FTP server.
    Store it in a local database.
    Remote
    Patents
    Patent
    Job
    Local
    Patents
    Thursday, February 28, 13
    

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38. @sandimetz Feb 2013
    FTP Server
    host:       localhost
    login:    
      anon
    password:  
    anon
    path:       Public/prod/
    filename:patents.csv
    Thursday, February 28, 13
    

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39. @sandimetz Feb 2013
    person_id,name,title
    cycler1,"Anti-­‐Gravity  Simulator","A  device  to  make  riding  uphill  easier"
    cycler1,"Exo-­‐Skello  Jello","An  after  dinner  treat  to  bulk  up  the  feeble"
    sleeper2,"Nap  Compressor","A  device  which  allows  a  30  minute  nap  is  just  3  minutes"
    Test Data
    FTP Server
    host:       localhost
    login:    
      anon
    password:  
    anon
    path:       Public/prod/
    filename:patents.csv
    Thursday, February 28, 13
    

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40. @sandimetz Feb 2013
    person_id,name,title
    cycler1,"Anti-­‐Gravity  Simulator","A  device  to  make  riding  uphill  easier"
    cycler1,"Exo-­‐Skello  Jello","An  after  dinner  treat  to  bulk  up  the  feeble"
    sleeper2,"Nap  Compressor","A  device  which  allows  a  30  minute  nap  is  just  3  minutes"
    Test Data
    FTP Server
    host:       localhost
    login:    
      anon
    password:  
    anon
    path:       Public/prod/
    filename:patents.csv
    Patent model object
    Thursday, February 28, 13
    

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41. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "downloads  the  csv  file  from  the  ftp  server"
         
       it  "asks  Patent  to  overwrite  existing  patents"
    end
    Thursday, February 28, 13
    

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42. @sandimetz Feb 2013
    PatentJob  Spec
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           job  =  PatentJob.new
           f  =  File.read(job.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
    Thursday, February 28, 13
    

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43. @sandimetz Feb 2013
    PatentJob  Spec
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           job  =  PatentJob.new
           f  =  File.read(job.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
    Thursday, February 28, 13
    

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44. @sandimetz Feb 2013
    PatentJob  Spec
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           job  =  PatentJob.new
           f  =  File.read(job.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
    Thursday, February 28, 13
    

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45. @sandimetz Feb 2013
    PatentJob  Spec
       
       it  "asks  Patent  to  overwrite  existing  patents"  do
           rows  =[{"person_id"=>"cycler1",  "name"=>"Anti-­‐Gravity  Simu
                         {"person_id"=>"cycler1",  "name"=>"Exo-­‐Skello  Jello"
                         {"person_id"=>"sleeper2",  "name"=>"Nap  Compressor",
           job  =  PatentJob.new
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    Thursday, February 28, 13
    

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46. @sandimetz Feb 2013
    PatentJob  Spec
       
       it  "asks  Patent  to  overwrite  existing  patents"  do
           rows  =[{"person_id"=>"cycler1",  "name"=>"Anti-­‐Gravity  Simu
                         {"person_id"=>"cycler1",  "name"=>"Exo-­‐Skello  Jello"
                         {"person_id"=>"sleeper2",  "name"=>"Nap  Compressor",
           job  =  PatentJob.new
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    Thursday, February 28, 13
    

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47. @sandimetz Feb 2013
    PatentJob  Spec
       
       it  "asks  Patent  to  overwrite  existing  patents"  do
           rows  =[{"person_id"=>"cycler1",  "name"=>"Anti-­‐Gravity  Simu
                         {"person_id"=>"cycler1",  "name"=>"Exo-­‐Skello  Jello"
                         {"person_id"=>"sleeper2",  "name"=>"Nap  Compressor",
           job  =  PatentJob.new
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    Thursday, February 28, 13
    

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48. @sandimetz Feb 2013
    PatentJob  Spec
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           job  =  PatentJob.new
           f  =  File.read(job.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
       it  "asks  Patent  to  overwrite  existing  patents"  do
           rows  =[{"person_id"=>"cycler1",  "name"=>"Anti-­‐Gravity  Simu
                         {"person_id"=>"cycler1",  "name"=>"Exo-­‐Skello  Jello"
                         {"person_id"=>"sleeper2",  "name"=>"Nap  Compressor",
           job  =  PatentJob.new
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    Thursday, February 28, 13
    

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49. @sandimetz Feb 2013
    class  Patent  <  ActiveRecord::Base
       def  self.overwrite(rows)
           #  lots  of  real  database  i/o
       end
    end
    Thursday, February 28, 13
    

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50. @sandimetz Feb 2013
    class  PatentJob
     
       def  run
           temp  =  download_file
           rows  =  parse(temp)
           update_patents(rows)
       end
     
       def  download_file
     
       def  parse(temp)
     
       def  update_patents(rows)
    end
    Thursday, February 28, 13
    

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51. @sandimetz Feb 2013
    class  PatentJob
     
       def  run
           temp  =  download_file
           rows  =  parse(temp)
           update_patents(rows)
       end
     
       def  download_file
     
       def  parse(temp)
     
       def  update_patents(rows)
    end
    Thursday, February 28, 13
    

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52. @sandimetz Feb 2013
    class  PatentJob
     
       def  run
           temp  =  download_file
           rows  =  parse(temp)
           update_patents(rows)
       end
     
       def  download_file
     
       def  parse(temp)
     
       def  update_patents(rows)
    end
    Thursday, February 28, 13
    

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53. @sandimetz Feb 2013
    class  PatentJob
     
       def  run
           update_patents(parse(download_file))
       end
     
       def  download_file
     
       def  parse(temp)
     
       def  update_patents(rows)
    end
    Thursday, February 28, 13
    

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54. @sandimetz Feb 2013
    class  PatentJob
     
       def  run
           update_patents(parse(download_file))
       end
     
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    Thursday, February 28, 13
    

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55. @sandimetz Feb 2013
    class  PatentJob
       def  run
           update_patents(parse(download_file))
       end
       
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
     
       def  parse(temp)
           CSV.read(temp,  :headers  =>  true).map(&:to_hash)
       end
     
       def  update_patents(rows)
           Patent.overwrite(rows)
       end
     
    end
    Entire PatentJob class
    Thursday, February 28, 13
    

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56. @sandimetz Feb 2013
    Remote
    Patents
    Patent
    Job
    Local
    Patents
    Thursday, February 28, 13
    

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57. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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58. @sandimetz Feb 2013
    I’m uneasy
    About the code
    What if the ftp host/user/password changes?
    What if other ftp’ing jobs are required?
    About the test
    I hate ftp’ing the le in every test
    Thursday, February 28, 13
    

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59. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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60. @sandimetz Feb 2013
    General Rule
    Leave it until you need it
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61. @sandimetz Feb 2013
    Resistance is a Resource
    Listen to your code
    Embrace the friction
    Fix the problem
    Thursday, February 28, 13
    

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62. @sandimetz Feb 2013
    Testing
    If testing seems hard,
    examine your design.
    Thursday, February 28, 13
    

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63. @sandimetz Feb 2013
    4 refactorings ...
    Thursday, February 28, 13
    

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64. @sandimetz Feb 2013
    Red Green Refactor
    Is it DRY?
    Does it have a one responsibility?
    Does everything in it change at the same rate?
    Does it depend on more stable things?
    Thursday, February 28, 13
    

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65. @sandimetz Feb 2013
    Red Green Refactor
    Is it DRY?
    Does it have a one responsibility?
    Does everything in it change at the same rate?
    Does it depend on more stable things?
    Thursday, February 28, 13
    

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66. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "downloads  the  csv  file  from  the  ftp  server"
         
       it  "asks  Patent  to  overwrite  existing  patents"
    end
    Thursday, February 28, 13
    

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67. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "downloads  the  csv  file  from  the  ftp  server"
         
       it  "asks  Patent  to  overwrite  existing  patents"
    end
    downloads and asks
    Thursday, February 28, 13
    

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68. @sandimetz Feb 2013
    Separate the Responsibilities
    Remote
    Patents Patent Job
    Local
    Patents
    Downloader
    Thursday, February 28, 13
    

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69. @sandimetz Feb 2013
    Separate the Responsibilities
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Thursday, February 28, 13
    

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70. @sandimetz Feb 2013
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Change PatentJob
    to use PatentDownloader
    Thursday, February 28, 13
    

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71. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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72. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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73. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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74. @sandimetz Feb 2013
    Dependency Injection creates a Seam
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Thursday, February 28, 13
    

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75. @sandimetz Feb 2013
    Patent Job
    Downloader
    Test Double
    Thursday, February 28, 13
    

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76. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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77. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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78. @sandimetz Feb 2013
    PatentJob  Spec
    describe  PatentJob  do
       it  "asks  Patent  to  overwrite  existing  patents"  do
           f        =  './spec/fixtures/patents.csv'
           rows  =  CSV.read(f,  :headers  =>  true).map(&:to_hash)
     
           downldr  =  double("Downloader")
           downldr.stub(:download_file).and_return(f)
     
           job  =  PatentJob.new(downldr)
           Patent.should_receive(:overwrite).with(rows)
           job.run
       end
    end
    Thursday, February 28, 13
    

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79. @sandimetz Feb 2013
       def  run
           temp  =  download_file
           rows  =  parse(temp)
           update_patents(rows)
    Thursday, February 28, 13
    

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80. @sandimetz Feb 2013
       def  run
           temp  =  download_file
       def  run
           temp  =  PatentDownloader.new.download_file
    Thursday, February 28, 13
    

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81. @sandimetz Feb 2013
       def  run
           temp  =  download_file
       def  run
           temp  =  PatentDownloader.new.download_file
    create a dependency
    Thursday, February 28, 13
    

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82. @sandimetz Feb 2013
       def  run
           temp  =  download_file
       def  run
           temp  =  PatentDownloader.new.download
    class  PatentJob
       attr_reader  :downloader
     
       def  initialize(downloader=PatentDownloader.new)
           @downloader  =  downloader
       end
     
       def  run
           temp  =  downloader.download_file
    Thursday, February 28, 13
    

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83. @sandimetz Feb 2013
       def  run
           temp  =  download_file
       def  run
           temp  =  PatentDownloader.new.download
    class  PatentJob
       attr_reader  :downloader
     
       def  initialize(downloader=PatentDownloader.new)
           @downloader  =  downloader
       end
     
       def  run
           temp  =  downloader.download_file
    inject a dependency
    Thursday, February 28, 13
    

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84. @sandimetz Feb 2013
       def  run
           temp  =  download_file
       def  run
           temp  =  PatentDownloader.new.download
    class  PatentJob
       attr_reader  :downloader
     
       def  initialize(downloader=PatentDownloader.new)
           @downloader  =  downloader
       end
     
       def  run
           temp  =  downloader.download_file
    depend on the message
    Thursday, February 28, 13
    

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85. @sandimetz Feb 2013
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Write PatentDownloader
    Thursday, February 28, 13
    

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86. @sandimetz Feb 2013
    PatentDownloader  Spec
    describe  PatentDownloader  do
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           upload_test_file('localhost',  'anon',  'anon',  'patents.csv
           
           downldr  =  PatentDownloader.new
           f  =  File.read(downldr.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
    end
    Thursday, February 28, 13
    

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87. @sandimetz Feb 2013
    PatentDownloader  Spec
    describe  PatentDownloader  do
       it  "downloads  the  csv  file  from  the  ftp  server"  do
           upload_test_file('localhost',  'anon',  'anon',  'patents.csv
           
           downldr  =  PatentDownloader.new
           f  =  File.read(downldr.download_file)
           f.should  have(250).characters
           f.should  include("just  3  minutes")
       end
    end
    Copied from PatentJob Spec
    Thursday, February 28, 13
    

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88. @sandimetz Feb 2013
    class  PatentDownloader
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    end
    Thursday, February 28, 13
    

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89. @sandimetz Feb 2013
    class  PatentDownloader
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    end
    Copied from PatentJob Class
    Thursday, February 28, 13
    

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90. @sandimetz Feb 2013
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Thursday, February 28, 13
    

    View Slide

91. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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92. @sandimetz Feb 2013
    Thursday, February 28, 13
    

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93. @sandimetz Feb 2013
    Red Green Refactor
    Is it DRY?
    Does it have a one responsibility?
    Does everything in it change at the same rate?
    Does it depend on more stable things?
    Thursday, February 28, 13
    

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94. @sandimetz Feb 2013
    Red Green Refactor
    Is it DRY?
    Does it have a one responsibility?
    Does everything in it change at the same rate?
    Does it depend on more stable things?
    Thursday, February 28, 13
    

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95. @sandimetz Feb 2013
    class  PatentDownloader
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    end
    Thursday, February 28, 13
    

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96. @sandimetz Feb 2013
    class  PatentDownloader
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    end
    FTP
    Thursday, February 28, 13
    

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97. @sandimetz Feb 2013
    class  PatentDownloader
       def  download_file
           temp  =  Tempfile.new('patents')
           tempname  =  temp.path
           temp.close
           Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
               ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
           end
           tempname
       end
    end
    FTP
    Configuration
    Thursday, February 28, 13
    

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98. @sandimetz Feb 2013
    Triangle of Responsibility Refactoring
    Extract
    Inject
    Refactor
    Thursday, February 28, 13
    

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99. @sandimetz Feb 2013
    Separate the Responsibilities
    Remote
    Patents Patent Job
    Local
    Patents
    Patent
    Downloader
    Con g
    Thursday, February 28, 13
    

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100. @sandimetz Feb 2013
     Separate the Responsibilities
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Patent
     Con g
     Thursday, February 28, 13
     

     View Slide

101. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Patent
     Con g
     Use double at this seam?
     Thursday, February 28, 13
     

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102. @sandimetz Feb 2013
     Write PatentConfig
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Patent
     Con g
     Thursday, February 28, 13
     

     View Slide

103. @sandimetz Feb 2013
     PatentConfig  Spec
        it  "knows  the  common  configuration  values"  do
            conf  =  PatentConfig.new
            conf.host.should          eql('localhost')
            conf.filename.should  eql('patents.csv')
            conf.login.should        eql('anon')
            conf.password.should  eql('anon')
        end
     Thursday, February 28, 13
     

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104. @sandimetz Feb 2013
     PatentConfig  Spec
        it  "knows  the  common  configuration  values"  do
            conf  =  PatentConfig.new
            conf.host.should          eql('localhost')
            conf.filename.should  eql('patents.csv')
            conf.login.should        eql('anon')
            conf.password.should  eql('anon')
        end
     Thursday, February 28, 13
     

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105. @sandimetz Feb 2013
     PatentConfig  Spec
        describe  "knows  the  correct  path  for"  do
            it  "production"    do
                conf  =  PatentConfig.new('production')
                conf.path.should  eql('Public/prod')
            end
      
            it  "test"  do
                conf  =  PatentConfig.new('test')
                conf.path.should  eql('Public/test')
            end
        end
     Thursday, February 28, 13
     

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106. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :env
      
        def  initialize(env='production')
            @env  =  env
        end
      
        def  host
            'localhost'
        end
      
        def  path
            "Public/"  +  ((env  ==  'production')  ?  'prod'  :  'test')
        end
      
        def  login
            'anon'
        end
        #  ...
     Thursday, February 28, 13
     

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107. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :env
      
        def  initialize(env='production')
            @env  =  env
        end
      
        def  host
            'localhost'
        end
      
        def  path
            "Public/"  +  ((env  ==  'production')  ?  'prod'  :  'test')
        end
      
        def  login
            'anon'
        end
        #  ...
     Yuck
     Thursday, February 28, 13
     

     View Slide

108. @sandimetz Feb 2013
     Refactor,
     not because
     you know the abstraction,
     but because
     you want to nd it.
     Thursday, February 28, 13
     

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109. @sandimetz Feb 2013
     defaults:  &defaults
        host:                              localhost
        login:                            anon
        password:                      anon
        filename:                      patents.csv
        path:                              Public/test
      
     test:
        <<:  *defaults
      
     development:
        <<:  *defaults
      
     production:
        <<:  *defaults
        path:                            Public/prod
     patent.yml
     Thursday, February 28, 13
     

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110. @sandimetz Feb 2013
     PatentConfig  Spec
        describe  "knows  the  correct  path  for"  do
            it  "production"    do
                conf  =  PatentConfig.new('production')
                conf.path.should  eql('Public/prod')
            end
      
            it  "test"  do
                conf  =  PatentConfig.new('test')
                conf.path.should  eql('Public/test')
            end
        end
     Thursday, February 28, 13
     

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111. @sandimetz Feb 2013
     PatentConfig  Spec
        describe  "knows  the  correct  path  for"  do
            it  "production"    do
                conf  =  PatentConfig.new({env:  'production'})
                conf.path.should  eql('Public/prod')
            end
      
            it  "test"  do
                conf  =  PatentConfig.new({env:  'test'})
                conf.path.should  eql('Public/test')
            end
        end
     Thursday, February 28, 13
     

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112. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
        end
        #  ...
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

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113. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
        end
        #  ...
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

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114. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
        end
        #  ...
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

     View Slide

115. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
        end
        #  ...
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

     View Slide

116. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
        end
        #  ...
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

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117. @sandimetz Feb 2013
     class  PatentConfig
          #  ...
        def  host
            data[env]['host']
        end
      
        def  login
            data[env]['login']
        end
      
        def  password
            data[env]['password']
        end
      
        def  path
            data[env]['path']
        end
        #  ...  
     end
     Thursday, February 28, 13
     

     View Slide

118. @sandimetz Feb 2013
     class  PatentConfig
          #  ...
        def  host
            data[env]['host']
        end
      
        def  login
            data[env]['login']
        end
      
        def  password
            data[env]['password']
        end
      
        def  path
            data[env]['path']
        end
        #  ...  
     end
     Yuck
     Thursday, February 28, 13
     

     View Slide

119. @sandimetz Feb 2013
        def  host
            data[env]['host']
        end    
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      “localhost”
                    end                                                  #  end
                EOS
            end
        end
     Thursday, February 28, 13
     

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120. @sandimetz Feb 2013
        def  host
            data[env]['host']
        end    
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      “localhost”
                    end                                                  #  end
                EOS
            end
        end
     Thursday, February 28, 13
     

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121. @sandimetz Feb 2013
        def  host
            data[env]['host']
        end    
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      “localhost”
                    end                                                  #  end
                EOS
            end
        end
     Thursday, February 28, 13
     

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122. @sandimetz Feb 2013
        def  host
            data[env]['host']
        end    
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      “localhost”
                    end                                                  #  end
                EOS
            end
        end
     Thursday, February 28, 13
     

     View Slide

123. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

     View Slide

124. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

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125. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     PatentConfig
     has nothing to do with
     Patents.
     Thursday, February 28, 13
     

     View Slide

126. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'patent.yml'}
        end
     end
     Thursday, February 28, 13
     

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127. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'config.yml'}
        end
     end
     Thursday, February 28, 13
     

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128. @sandimetz Feb 2013
     class  PatentConfig
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'config.yml'}
        end
     end
     Thursday, February 28, 13
     

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129. @sandimetz Feb 2013
     class  Configuration
        attr_reader  :data,  :env
      
        def  initialize(args={})
        def  define_methods_for_environment
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'config.yml'}
        end
     end
     Thursday, February 28, 13
     

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130. @sandimetz Feb 2013
     class  Configuration
        attr_reader  :data,  :env
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
            define_methods_for_environment
        end
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      “localhost”
                    end                                                  #  end
                EOS
            end
        end
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'config.yml'}
        end
     end
     Entire Configuration class
     Thursday, February 28, 13
     

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131. @sandimetz Feb 2013
     Configuration
     is an abstraction
     has a single responsibility
     is open for extension
     and closed for modi cation
     Thursday, February 28, 13
     

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132. @sandimetz Feb 2013
     Use Configuration in PatentDownloader
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Con guration
     Thursday, February 28, 13
     

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133. @sandimetz Feb 2013
     class  PatentDownloader
        def  download_file
            temp  =  Tempfile.new('patents')
            tempname  =  temp.path
            temp.close
            Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
                ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
            end
            tempname
        end
     end
     Last we saw
     Thursday, February 28, 13
     

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134. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new('patents')
            tempname  =  temp.path
            temp.close
            Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
                ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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135. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new('patents')
            tempname  =  temp.path
            temp.close
            Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
                ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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136. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new('patents')
            tempname  =  temp.path
            temp.close
            Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
                ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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137. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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138. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Con guration
     Thursday, February 28, 13
     

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139. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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140. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     PatentDownloader
     has nothing to do with
     Patents.
     Thursday, February 28, 13
     

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141. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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142. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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143. @sandimetz Feb 2013
     class  PatentDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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144. @sandimetz Feb 2013
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     Thursday, February 28, 13
     

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145. @sandimetz Feb 2013
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new({filename:  'patent.yml'}))
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),
                                                    tempname)
            end
            tempname
        end
     end
     ???
     Thursday, February 28, 13
     

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146. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Patent
     Downloader
     Con guration
     Thursday, February 28, 13
     

     View Slide

147. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Con guration
     Thursday, February 28, 13
     

     View Slide

148. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Ftp
     Downloader
     Con guration
     Thursday, February 28, 13
     

     View Slide

149. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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150. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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151. @sandimetz Feb 2013
     Red Green Refactor
     Is it DRY?
     Does it have a one responsibility?
     Does everything in it change at the same rate?
     Does it depend on more stable things?
     Thursday, February 28, 13
     

     View Slide

152. @sandimetz Feb 2013
     Red Green Refactor
     Is it DRY?
     Does it have a one responsibility?
     Does everything in it change at the same rate?
     Does it depend on more stable things?
     Thursday, February 28, 13
     

     View Slide

153. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     Thursday, February 28, 13
     

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154. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     PatentJob depends on FtpDownloader
     Thursday, February 28, 13
     

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155. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     FtpDownloader depends on Configuration
     Thursday, February 28, 13
     

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156. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     FtpDownloader  also
     depends on patent.yml
     Thursday, February 28, 13
     

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157. @sandimetz Feb 2013
     Less More
     Likelihood of Change
     Configuration
     Ftp
     Downloader
     PatentJob patent.yml
     Thursday, February 28, 13
     

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158. @sandimetz Feb 2013
     Less More
     Likelihood of Change
     Configuration
     PatentJob patent.yml
     Always depend on things to your left
     Ftp
     Downloader
     Thursday, February 28, 13
     

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159. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     Thursday, February 28, 13
     

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160. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     Thursday, February 28, 13
     

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161. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(downloader=FtpDownloader.new)
            @downloader  =  downloader
        end
     class  FtpDownloader
        attr_reader  :config
        def  initialize(config=Configuration.new(
                                                      {filename:  'patent.yml'}))
            @config  =  config
        end
     class  Configuration
        attr_reader  :data,  :env  
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
     patent.yml
     v
     Thursday, February 28, 13
     

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162. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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163. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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164. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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165. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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166. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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167. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
     Thursday, February 28, 13
     

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168. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Ftp
     Downloader
     Con guration
     Thursday, February 28, 13
     

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169. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Ftp
     Downloader
     Con guration
     Thursday, February 28, 13
     

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170. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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171. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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172. @sandimetz Feb 2013
     Red Green Refactor
     Is it DRY?
     Does it have a one responsibility?
     Does everything in it change at the same rate?
     Does it depend on more stable things?
     Thursday, February 28, 13
     

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173. @sandimetz Feb 2013
     Red Green Refactor
     Is it DRY?
     Does it have a one responsibility?
     Does everything in it change at the same rate?
     Does it depend on more stable things?
     Thursday, February 28, 13
     

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174. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
     Thursday, February 28, 13
     

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175. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
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176. @sandimetz Feb 2013
     defaults:  &defaults
        host:                              localhost
        login:                            anon
        password:                      anon
        filename:                      patents.csv
        path:                              Public/test
        downloader_class:      FtpDownloader
      
     test:
        <<:  *defaults
      
     development:
        <<:  *defaults
      
     production:
        <<:  *defaults
        path:                            Public/prod
     patent.yml
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177. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      FtpDownloader.new(config)
        end
      
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178. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
      
        def  initialize(opts={})
            config              =  opts[:config]          ||=  \
                                      Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                      config.connector_class.const_get.new(config)
        end
      
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179. @sandimetz Feb 2013
     Remote
     Patents Patent Job
     Local
     Patents
     Ftp
     Downloader
     Con guration
     Thursday, February 28, 13
     

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180. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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181. @sandimetz Feb 2013
     Before
     Thursday, February 28, 13
     

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182. @sandimetz Feb 2013
     class  PatentJob
        def  run
            update_patents(parse(download_file))
        end
        
        def  download_file
            temp  =  Tempfile.new('patents')
            tempname  =  temp.path
            temp.close
            Net::FTP.open('localhost',  'anon',  'anon')  do  |ftp|
                ftp.getbinaryfile('Public/prod/patents.csv',  tempname)
            end
            tempname
        end
      
        def  parse(temp)
            CSV.read(temp,  :headers  =>  true).map(&:to_hash)
        end
      
        def  update_patents(rows)
            Patent.overwrite(rows)
        end
      
     end
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183. @sandimetz Feb 2013
     After
     Thursday, February 28, 13
     

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184. @sandimetz Feb 2013
     class  PatentJob
        attr_reader  :downloader
        def  initialize(opts={})
            config            =  opts[:config]          ||=  \  
                                        Configuration.new({filename:  'patent.yml'})
            @downloader  =  opts[:downloader]  ||=  \
                                        config.connector_class.const_get.new(config)
        end
      
        def  run
            update_patents(parse(downloader.download_file))
        end
      
        def  parse(temp)
            CSV.read(temp,  :headers  =>  true).map(&:to_hash)
        end
      
        def  update_patents(rows)
            Patent.overwrite(rows)
        end
      
     end
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185. @sandimetz Feb 2013
     class  FTPDownloader
        attr_reader  :config
        def  initialize(config)
            @config  =  config
        end
        def  download_file
            temp  =  Tempfile.new(config.filename)
            tempname  =  temp.path
            temp.close
            Net::FTP.open(config.host,  
                                        config.login,  
                                        config.password)  do  |ftp|
                ftp.getbinaryfile(File.join(config.path,  config.filename),                
                                                    tempname)
            end
            tempname
        end
     end
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186. @sandimetz Feb 2013
     class  Configuration
        attr_reader  :data,  :env
        def  initialize(args={})
            args    =  defaults.merge(args)
            @env    =  args[:env]
            @data  =  YAML::load_file(File.join(args[:path],
                                                                                args[:filename]))
            define_methods_for_environment
        end
        def  define_methods_for_environment
            data[env].each  do  |name,  value|
                instance_eval  <<-­‐EOS
                    def  #{name}                                  #  def  host
                        "#{value}"                                #      data[env]['host']
                    end                                                  #  end
                EOS
            end
        end
        def  defaults
            {env:            'production',
              path:          File.join('config'),
              filename:  'config.yml'}
        end
     end
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187. @sandimetz Feb 2013
     ActTraining
     RequiredUserNoti cation
     OESO
     RCC
     PayrollFunding
     ActiveKeyPerson
     Award
     Many New Jobs
     Thursday, February 28, 13
     

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188. @sandimetz Feb 2013
     SFTP
     Web Scraper via Mechanize
     Sql
     File Copy
     Many New Downloaders
     Thursday, February 28, 13
     

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189. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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190. @sandimetz Feb 2013
     The future is coming
     Thursday, February 28, 13
     

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191. @sandimetz Feb 2013
     Let’s enjoy it
     Thursday, February 28, 13
     

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192. @sandimetz Feb 2013
     Thursday, February 28, 13
     

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193. Thanks
     Sandi Metz
     @sandimetz
     https://joind.in/7876
     Thursday, February 28, 13
     

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194. http://www. ickr.com/photos/freshwater2006/693945631/
     http://www. ickr.com/photos/shainerin/3033898043/
     http://www. ickr.com/photos/87255087@N00/4184665341/
     http://www. ickr.com/photos/robwallace/154301240/
     http://www. ickr.com/photos/jpstanley/239788572/
     http://www. ickr.com/photos/nationalgalleries/3110282571/
     http://www. ickr.com/photos/familymwr/5112367957/
     http://www. ickr.com/photos/marine_corps/5132830788/
     http://www. ickr.com/photos/atolsma/6945061383/
     http://www. ickr.com/photos/whiteafrican/409072927/
     http://www. ickr.com/photos/tabor-roeder/5652475824/in/photostream/
     http://www. ickr.com/photos/76526962@N00/7982132871/in/photostream/
     http://www. ickr.com/photos/johnspooner/2899977876/
     http://www. ickr.com/photos/bike/7721413266/
     http://www. ickr.com/photos/stevengrayphotography/6893448452/
     http://www. ickr.com/photos/thelearningcurvedotca/5793648808/
     http://www. ickr.com/photos/whateverthing/241245603/
     Photo Credits
     Thursday, February 28, 13
     

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195. @sandimetz Feb 2013
     http://poodr.info
     Thursday, February 28, 13
     

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196. @sandimetz Feb 2013
     Hot
     off
     the
     press
     http://poodr.info
     Thursday, February 28, 13
     

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197. Questions?
     https://joind.in/7876
     Thursday, February 28, 13
     

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198. @sandimetz Feb 2013
     http://poodr.info
     Thursday, February 28, 13
     

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