Concerning 'Application'

Rails refactoring technique using ActiveSupport::Concern, talked on RubyKaigi 2013.

Transcript

1. Concerning
   ‘Applications’
   Kyosuke MOROHASHI (@moro)
   RubyKaigi 2013, May 31, 2013
   

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2. ॾڮګհ(@moro)
   Kyosuke MOROHASHI
   

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5. 31st
   on leaderboard
   

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6. Background
   

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7. Rails applications are applied
   to complex real-life problems.
   

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8. Many rails users worry about
   the ‘Fat model’ problem.
   

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9. ✓ One of solutions is the
   technique of ‘Concern’s, which
   divides model behavior into
   small units.
   ✓ implemented as
   ActiveSupport::Concern
   

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10. What is Rails’
    ActiveSupport::
    Concern ?
    

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11. Ruby’s Module
    extension by Rails
    

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12. ✓ automatically extends own
    ClassMethods
    module if exists.
    ✓ provides included {}
    callback for declarative
    methods.
    

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13. gist:moro/5652724
    module Censorable
    extend ActiveSupport::Concern
    included do
    has_many :monitor_requests, as: :entity,
    validates :censor_status, inclusion: Censorable
    end
    module ClassMethods
    def censor_passed
    where(status: Censorable::PASSED_STATUSES)
    end
    end
    def censor_passed?
    censor_status.passed?
    end
    

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14. What’s nice about
    ActiveSupport::Concern
    ?
    

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15. ✓ Provides a convention to write:
    ✓ Instance methods
    ✓ Class methods
    ✓ Configuration & customization
    by declarative methods.
    

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16. became first class citizen in
    Rails 4 <3 <3 <3
    

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17. ActiveSupport::
    Concern is a nice
    Rails’ module extension.
    

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18. What should
    we Concern
    about?
    

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19. Models’ common
    behaviors
    

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20. ✓ Users can tag the
    {question|answer}.
    ✓ Users can comment on the
    {question|answer}.
    ✓ Service providers must censor user-
    posted {question|answer}’s content.
    

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21. class Question < AR::Base
    include Taggable
    include Commentable
    include Censorable
    # and question specific definitions..
    end
    class Answer < AR::Base
    include Taggable
    include Commentable
    include Censorable
    # and question answer definitions..
    end
    

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22. Nested resource's
    parent.
    

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23. # question and answers that the user has
    # /users/:user_id/questions
    # /users/:user_id/answers
    resources :users do
    resources :questions
    resources :answers
    end
    

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24. module UsersResource
    extend ActiveSupport::Concern
    included do
    helper_method :owner
    hide_action :owner
    end
    private
    def owner
    @_owner ||=
    User.where(id: params[:user_id]).first
    end
    end
    

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25. use AS::Concern to
    extract common
    behaviors.
    

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26. How do we use
    AS::Concern
    nicely?
    

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27. Keep it a GLUE
    

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28. ✓ Add only a few methods to a
    base class.
    ✓ Keep ‘Loose Coupling’
    between Concern and
    models.
    

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29. gist:moro/5652724
    module Censorable
    extend ActiveSupport::Concern
    (skip)
    def feedback_monitor_judge(status)
    if PASSED_STATUSES.include?(status)
    ....
    else
    ....
    end
    end
    def request_monitoring!
    req = monitor_requests.create!(content: monitor
    res = post_monitor_request(req)
    unless res.code == '200'
    raise Censorable::MonitorRequestFailed.new(re
    end
    Bad case
    

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30. gist:moro/5652724
    module Censorable
    extend ActiveSupport::Concern
    (skip)
    def request_monitoring!
    MonitorRequest.submit(self)
    end
    end
    Good case
    

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31. gist:moro/5652724
    class MonitorRequest < ActiveRecord::Base
    class << self
    def submit(entity)
    req = create!(entity: entity, content: monito
    res = post_monitor_request(req)
    unless res.code == '200'
    raise Censorable::MonitorRequestFailed.new(
    end
    end
    end
    end
    Good case
    

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32. Tests become
    more obvious.
    

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33. gist:moro/5652724
    describe Censorable do
    let(:question) { create(:question) }
    before do
    question.request_monitoring!
    end
    specify do
    MonitoringRequest.
    should have(1).record
    end
    end
    Bad case
    

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34. gist:moro/5652724
    describe MonitoringRequest do
    let(:question) { create(:question) }
    before do
    MonitoringRequest.submit(question)
    end
    specify do
    MonitoringRequest.
    should have(1).record
    end
    end Good case
    

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35. How to glue
    class specific
    behavior?
    

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36. ✓ Plain old conditional branch
    ✓ Template methods
    

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37. gist:moro/5652724
    class MonitorRequest < ActiveRecord::Base
    class << self
    def monitoring_content(obj)
    case obj
    when Question
    [obj.title, obj.body].join("\n\n")
    when Answer
    entity.body
    end
    end
    end
    end
    Plain old conditional branch
    

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38. PROS: Less effect on base class.
    CONS: Too naive.
    Plain old conditional branch
    

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39. gist:moro/5652724
    class MonitorRequest < ActiveRecord::Base
    class << self
    def submit(entity)
    content = entity.monitoring_content
    ...
    class Question < AR::Base
    def monitoring_content
    [title, body].join("\n\n")
    end
    end
    class Answer < AR::Base
    def monitoring_content; body; end
    end
    Template method
    

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40. PROS: Acquires polymorphism.
    CONS: pollutes base classes.
    Template method
    

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41. Keep Concern a thin, glue layer.
    But still something is wrong with
    interface with base class...
    

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42. in Ruby 2.0
    Concern meets
    Refinements
    

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43. “Refinements are intended
    to restrict the impact of
    monkey patching to a
    certain scope
    http://jp.rubyist.net/magazine/?Ruby200SpecialEn-refinement
    @shugomaeda says:
    

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44. Restrict the impact of
    glue code’s template
    method.
    

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45. gist:moro/5652724
    module Censorable
    module MonitoringContent
    refine Question do
    def monitoring_content
    [title, body].join("\n\n")
    end
    end
    refine Answer do
    def monitoring_content; body ; end
    end
    end
    end Refinements
    

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46. gist:moro/5652724
    using Censorable::MonitoringContent
    class MonitorRequest < ActiveRecord::Base
    class << self
    def submit(entity)
    content = entity.monitoring_content
    ...
    Refinements
    

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47. BTY: Concern as a service layer glue?
    ✓ Refinements let us define:
    ✓ context specific extensions.
    ✓ multi-classes ext. in one place.
    

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48. BTY: Concern as a service layer glue?
    ✓ Concern could:
    ✓ provide namespace to the
    extensions.
    ✓ glue base classes and the
    extensions.
    

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49. Ruby 2.0’s refinements are so
    great that we can extract
    concerns nicely with them.
    

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50. Wrapping up
    

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51. ✓ AS::Concern is a way to keep
    your application clean.
    ✓ I talked about a way to use it
    nicely :-)
    

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52. ActiveSupport::Concern
    is not ‘off the Rails’.
    

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53. It’s a supporter, like a bicycle:
    it helps your journey where there's no
    common rails.
    

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54. Acknowledgements
    ✓ All of Ruby community: especially Ruby team , Rails team,
    RubyKaigi staffs and you.
    ✓ My clients, colleagues, friends and family.
    ✓ Nice material authors:
    ✓ http://good-wallpapers.com/misc/22337
    ✓ http://www.fontspace.com/pete-klassen/ringbearer
    ✓ http://subtlepatterns.com/
    ✓ http://www.flickr.com/photos/dailyinvention/23126614/
    ✓ http://www.flickr.com/photos/bdamgaard/510134092/
    

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