Forget about classes, welcome objects

Transcript

1. 1.

   Alexandre de Oliveira (@kurko) Forget about classes,
   welcome objects

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   None
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   None
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   Perspective

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   Alan Kay

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   “Point of view is worth 80 IQ points” - Alan

   Kay
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   None
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   VI

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   6

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    Reality as we conceive it

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    Source: http://2.bp.blogspot.com/_EussjcZFO-c/SW1ITAQSlRI/AAAAAAAAAZY/Zmn7X88qBHk/s400/Princess+Anne+says+hello.jpg

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    OOP?

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    “OOP to me means only messaging, local retention and protection

    and hiding of state” Alan Kay
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    None
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    None
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    None
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    Complexity http://dougbelshaw.com/presentations/2012/ILTA/assets/complexity.jpg

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    Problem #1: disorganisation

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    ONE BIG OBJECT™

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    many small objects collaborating with each other

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    http://20px.com/wp-content/uploads/2013/02/unicorn_pooping_a_rainbow_20px.jpg

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    such complexity, much wow

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    http://adeviantman.deviantart.com/art/Pink-Fluffy-Unicorns-Dancing-On-Rainbows-315632047

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    Problem #2: procedural code

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    Domain Organization Project Stories Members Importing projects from Pivotal Tracker

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    class ImportationService ! ! ! ! ! ! ! !

    ! ! end
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    class ImportationService def process orgs = Organizations.new(client).import end end

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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end ! ! ! end end
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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end projects.each do |project| Members.new(client).import end end end
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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end projects.each do |project| Members.new(client).import Stories.new(client).import end end end
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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end projects.each do |project| Members.new(client).import Stories.new(client).import unless client.github? end end end
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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end projects.each do |project| Members.new(client).import Stories.new(client).import unless client.github? end end end Beginning of the end
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    def process_extension!(extension_price, options={}) options.reverse_merge!({ :credit_card => user.default_credit_card, :billing_address => options[:credit_card].try(:billing_address)

    || user.default_address, :store => order.store, :tax => tax, :days => 14, :buyout => false }) ! creator = options[:creator] return process_extension_without_charge!(options) if options[:no_charge] ! response = Payment::Gateway.charge!( extension_price.cents.to_f/100, options[:credit_card].ext_cc_id, self.user.id, options[:store].try(:address).try(:country) ) ! # payment failed unless response[:ext_transaction_id].present? self.order.order_responses.create(:message => response[:error]) self.errors.add(:base, response[:error]) return false end ! data = { :ext_transaction_id => response[:ext_transaction_id], :parent_order_id => self.order.id, :parent_order_item_id => self.id, :ccauth_reply_authorization_code => response[:ccauth_reply_authorization_code] } ! if options[:buyout] # it's a buyout OrderTransaction.buyout!( self.order.currency, extension_price.cents - options[:tax].cents, self, data, creator ) ! OrderTransaction.tax_charged!( self.order.currency, options[:tax].cents, self, data, creator ) ! process_convert_to_purchase! ! else # it's a regular extension begin OrderTransaction.extension!( "#{options[:days]} days", self.order.currency, extension_price.cents - options[:tax].cents, self, data, creator ) OrderTransaction.tax_charged!( self.order.currency, options[:tax].cents, self, data, creator ) # Increment extension days for current Item self.increment(:extension_days, options[:days]) self.update_attribute(:state, 'shipped_with_customer_extended') OrderItemMailer.rental_extended(self).deliver rescue Net::SMTPSyntaxError => exception Airbrake.notify( :error_class => exception.class.to_s, :error_message => "Bad Email Address Format. Order Item: #{self.id}. Email: #{self.order.user.email}", :parameters => self.attributes, :backtrace => caller) end end ! return true end 100+ LoC Real Code™
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    Flattened Domain Organization Project Stories Members

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg Curiosity

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg 2.5 M LoC

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg Written in C

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg Completely OOP

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    WAT http://www.gazetadopovo.com.br/blogs/cinema-em-casa/wp-content/uploads/sites/30/2013/05/short2circuit2654.jpg

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    http://www.wired.com/wp-content/uploads/blogs/design/wp-content/uploads/2012/08/MSL-Rover-NX-CAD-model.jpg

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    Path Finder Radio receiver Sample Analysis Descent Imager ChemCam UV

    Sensor Engine Wheels
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    Component 1 Component 2 Component 3 Component n Message Queue

    Component 4 Component 5 Component 6 Component z
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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg • Lots of messages • No mutexes, no transactional

    memory • Complete isolation between modules
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    OOP is not about Objects http://3.bp.blogspot.com/-MwiEp-63Qro/TrQvxNtQbBI/AAAAAAAABNc/6c8bAI0kdAM/s1600/facteur.jpg

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    It’s about the Message.

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg Objects: what the system is. Messages: what the system

    does.
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    http://x4.fjcdn.com/comments/Oh+_a70c957887dd1e4f713fb14db1dc582a.jpg Likely built with OOP

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg NASA basically rewrote Erlang

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    http://cdn.cantechletter.com/wp-content/uploads/2012/09/NASA-Mars-Rover.jpg "Erlang might be the only object oriented language” -

    Joe Armstrong
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    Person calls Pencil#write 1/2 Developer’s point of view Person Pencil

    Pen
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    2/2 Object’s point of view someone someone else pay() pay()

    someone else
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    None
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    None
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    Objects = 2 Complexity = 1

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    Objects = 3 Complexity = 3

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    Objects = 6 Complexity = ?

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    Objects = 6 Complexity = 15

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    How to stop complexity

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    How to stop wasting time complexity

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    How to stop wasting money wasting time complexity

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    “The key to scalability lies in how messaging is actually

    done. The key to abstraction and compactness lies in a felicitous combination of design and mathematics." ! - Alan Kay
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    Constructal Law

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    http://upload.wikimedia.org/wikipedia/commons/f/f6/Bright_green_tree_-_Waikato.jpg

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    http://hqwallpapersplus.com/wp-content/uploads/2013/09/Snowflake-Pictures-11.jpg

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    http://readywisconsin.wi.gov/lightning/images/Lightning_1.jpg

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    http://marjorymejia.com/wp-content/uploads/2012/10/800px-Mouths_of_amazon_geocover_1990.png

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    http://lh3.ggpht.com/-MgYN_UYAeCQ/S3xhh3CvNlI/AAAAAAAAAIU/j9rFK8ew7cE/900898-Resin%2520cast%2520human%2520lungs%2520and%2520bronchial%2520tree.jpg

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    http://www.spatialcomplexity.info/files/2012/12/morphology-map.png

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    Objects = 6 Complexity = 15

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    Objects = 7 Complexity = 8

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    C O Before After Architecture comparison

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    Example Module Module Module Computer Computer Computer

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    Danger, Will Robinson! Módulo Módulo Módulo A B

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    Effects ! 1. decreased complexity 2. simpler code 3. lower

    cognitive load 4. less wasted $$$
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    class ImportationService def process orgs = Organizations.new(client).import orgs.each do |org|

    projects = Projects.new(org).import end projects.each do |project| Members.new(client).import Stories.new(client).import end end end Before
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    module RemoteService class Organizations def initialize(remote_client) @client = remote_client end

    def import import_organizations Projects.new(@client).import end ! private ! def import_organizations organizations = @client.organizations OrganizationsTable.new(organizations).save end end end After
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    module RemoteService class Projects def initialize(remote_client) @client = remote_client end

    def import import_projects Members.new(@client).import Stories.new(@client).import end ! private ! def import_projects projects = @client.projects ProjectsTable.new(projects).save end end end
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    module RemoteService class Projects def initialize(remote_client) @client = remote_client end

    def import import_projects Members.new(@client).import Stories.new(@client).import unless @client.github? end ! private ! def import_projects projects = @client.projects ProjectsTable.new(projects).save end end end What now?
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    module PivotalTracker class Client def organizations HTTParty.get(‘url’).map { |i| Response::Organization.new(i)

    } end ! def projects HTTParty.get(‘url2’).map { |i| Response::Project.new(i) } end ! def members HTTParty.get(‘url3’).map { |i| Response::Member.new(i) } end ! def stories HTTParty.get(‘url4’).map { |i| Response::Story.new(i) } end end end
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    module Github class Client def organizations HTTParty.get(‘url’).map { |i| Response::Organization.new(i)

    } end ! ! ! ! ! ! ! ! ! ! ! ! end end
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    module Github class Client def organizations HTTParty.get(‘url’).map { |i| Response::Organization.new(i)

    } end ! def projects HTTParty.get(‘url2’).map { |i| Response::Project.new(i) } end ! ! ! ! ! ! ! ! end end
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    module Github class Client def organizations HTTParty.get(‘url’).map { |i| Response::Organization.new(i)

    } end ! def projects HTTParty.get(‘url2’).map { |i| Response::Project.new(i) } end ! def members HTTParty.get(‘url3’).map { |i| Response::Member.new(i) } end ! ! ! ! end end
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    module Github class Client def organizations HTTParty.get(‘url’).map { |i| Response::Organization.new(i)

    } end ! def projects HTTParty.get(‘url2’).map { |i| Response::Project.new(i) } end ! def members HTTParty.get(‘url3’).map { |i| Response::Member.new(i) } end ! def stories [] end end end
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    Effects ! 1. flexible code 2. less changes 3. Open/Closed

    principle 4. less wasted $$$
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    What about debugging?

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    What about debugging? Module Module Module Computer Computer Computer

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    Binary Search Module Module Module Computer Computer Computer

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    Binary Search Module Module Computer Computer Computer has the bug

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    Instrumentation Module Computer Tests

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    Write great code

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    Embrace OO

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    “It (OOP) can be done in Smalltalk and in LISP”

    Alan Kay
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    Thank you!

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    Resources • http://computinged.wordpress.com/2010/09/15/alan-kay-on-motis-objects-ever-cacm-article/ • http://jlouisramblings.blogspot.com/2012/08/getting-25-megalines-of-code-to-behave.html