Concerned about Concerns?

Presented at LRUG (London) on September 2013

With Rails 4, Concerns have become the “official” solution to the big-models problem. However, there's a fair amount of controversy about this topic in the community. Not everyone is convinced that Concerns are the “right“ solution to the problem of AR models becoming too big.

In this talk we will see what Rails Concerns are and how can we use them to keep our models fit. More interestingly, we'll discuss the trade-offs of this technique, the different views in the community and a couple of alternatives.

Transcript

1. $PODFSOFE
   BCPVU
   $PODFSOT CZ
   -VJTNJ
   $BWBMMÉ
2. require_dependency,'topic_view' require_dependency,'rate_limiter' require_dependency,'text_sentinel' require_dependency,'text_cleaner' class,Topic,<,ActiveRecord::Base ,,include,ActionView::Helpers ,,include,RateLimiter::OnCreateRecord ,,def,self.max_sort_order ,,,,2**31,7,1 https://github.com/discourse/discourse/blob/master/app/models/topic.rb
3. require_dependency,'slug' require_dependency,'avatar_lookup' require_dependency,'topic_view' require_dependency,'rate_limiter' require_dependency,'text_sentinel' require_dependency,'text_cleaner' class,Topic,<,ActiveRecord::Base ,,include,ActionView::Helpers ,,include,RateLimiter::OnCreateRecord ,,def,self.max_sort_order ,,,,2**31,7,1 ,,end ,,def,self.featured_users_count ,,,,4 ,,end ,,versioned,if:,:new_version_required? ,,acts_as_paranoid ,,after_recover,:update_flagged_posts_count ,,after_destroy,:update_flagged_posts_count ,,rate_limit,:default_rate_limiter ,,rate_limit,:limit_topics_per_day https://github.com/discourse/discourse/blob/master/app/models/topic.rb
4. end https://github.com/discourse/discourse/blob/master/app/models/topic.rb 
   -0$ BOE
   UIBU`T
   OPU
   UPP
   NVDI
5. #JH
   .PEFMT
6. 'BU
   .PEFMT
7. (JHBOUJD
   .PEFMT
8. 8IZ
   BSF
   UIFZ
   CBE
10. -PX
    $PIFTJPO
11. 5JHIU
    $PVQMJOH
12. #FDBVTF
    {{your_favourite_OO_guru}}
    TBZT
    TP
13. 8IZ
    BSF
    UIFZ
    CBE
    JO
    QSBDUJDBM
    UFSNT
    QMFBTF
14. !!class!Article!<!ActiveRecord::Base !!!!attr_accessor!:moderation_option ! !!!!attr_accessible!:text,!:reply_to_i ! !!!!belongs_to!:topic !!!!belongs_to!:user,!!!!!:class_name! !!!!belongs_to!:reply_to,!:class_name!
15. !!!belongs_to!:user,!!!!!:class_name!=>!Fore !!!belongs_to!:reply_to,!:class_name!=>!"Pos !!!has_many!:replies,!:class_name!!=>!"Post" !!!!!!!!!!!!!!!!!!!!!!:foreign_key!=>!"reply !!!!!!!!!!!!!!!!!!!!!!:dependent!!!=>!:nulli !!! !!!has_many!:taggings !!!has_many!:tags,!:through!=>!:taggings !!!validates!:text,!:presence!=>!true !!!delegate!:forum,!:to!=>!:topic !!!after_create!:set_topic_last_post_at !!!after_create!:skip_pending_review
16. !!!!end !!!!def!pending_review !!!!!!where!:state!=>!'pending_review' !!!!end !!!!def!spam !!!!!!where!:state!=>!'spam' !!!!end !!!! !!!!def!tagged_with(tag) !!!!!!joins(:taggings!=>!:tags).where(:tags!=>!{!:name!=>!tag!}) !!!!end !!!!def!visible !!!!!!joins(:topic).where(:forem_topics!=>!{!:hidden!=>!false!}) !!!!end !!end !! !!def!tag_names=(tag_list) !!!!assign_tag_list!tag_list !!end !!private
17. !!!!!end !!!end !!! !!!def!tag_names=(tag_list) !!!!!assign_tag_list!tag_list !!!end !!!private !!!def!subscribe_replier !!!!!if!topic!&&!user
18. ! !!!!def!blacklist_user !!!!!!user.update_attribute(:forem_state,!"spam")!if!user !!!!end !!!! !!!!def!assign_tag_list(tag_list) !!!!!!tag_names!=!tag_list.gsub(/\s+/,!"").split(",") !!!!!!existing!=!self.tags.map!{|t|!t.name!} !!!!!!(existing!@!tag_names).each!do!|name| !!!!!!!!self.tags.delete!Tag.find_by_name(name) !!!!!!end !!!!!!tag_names.each!do!|name| !!!!!!!!self.tags!<<!Tag.find_or_create_by_name(name) !!!!!!end! !!!!end !!end
19. !!class!Article!<!ActiveRecord::Base !!!!attr_accessor!:moderation_option ! !!!!attr_accessible!:text,!:reply_to_id,!:tag_names ! !!!!belongs_to!:topic !!!!belongs_to!:user,!!!!!:class_name!=>!Forem.user_class.to_s !!!!belongs_to!:reply_to,!:class_name!=>!"Post" ! !!!!has_many!:replies,!:class_name!!=>!"Post", !!!!!!!!!!!!!!!!!!!!!!!:foreign_key!=>!"reply_to_id", !!!!!!!!!!!!!!!!!!!!!!!:dependent!!!=>!:nullify !!!! !!!!has_many!:taggings !!!!has_many!:tags,!:through!=>!:taggings ! !!!!validates!:text,!:presence!=>!true ! !!!!delegate!:forum,!:to!=>!:topic ! !!!!after_create!:set_topic_last_post_at !!!!after_create!:skip_pending_review !!!!after_save!:email_topic_subscribers ! !!!!class!<<!self !!!!!!def!by_created_at !!!!!!!!order!:created_at !!!!!!end ! !!!!!!def!pending_review !!!!!!!!where!:state!=>!'pending_review' !!!!!!end ! !!!!!!def!spam !!!!!!!!where!:state!=>!'spam' !!!!!!end !!!!!! !!!!!!def!tagged_with(tag) !!!!!!!!joins(:taggings!=>!:tags).where(:tags!=>!{!:name!=>!tag!}) !!!!!!end ! !!!!!!def!visible !!!!!!!!joins(:topic).where(:forem_topics!=>!{!:hidden!=>!false!}) !!!!!!end !!!!end !!!! !!!!def!tag_names=(tag_list) !!!!!!assign_tag_list!tag_list !!!!end ! !!!!private ! !!!!def!subscribe_replier !!!!!!if!topic!&&!user !!!!!!!!topic.subscribe_user(user.id) !!!!!!end !!!!end ! !!!!def!set_topic_last_post_at !!!!!!topic.update_attribute(:last_post_at,!created_at) !!!!end ! !!!!def!blacklist_user !!!!!!user.update_attribute(:forem_state,!"spam")!if!user !!!!end !!!! !!!!def!assign_tag_list(tag_list) !!!!!!tag_names!=!tag_list.gsub(/\s+/,!"").split(",") !!!!!!existing!=!self.tags.map!{|t|!t.name!} !!!!!!(existing!@!tag_names).each!do!|name| !!!!!!!!self.tags.delete!Tag.find_by_name(name) !!!!!!end !!!!!!tag_names.each!do!|name| !!!!!!!!self.tags!<<!Tag.find_or_create_by_name(name) !!!!!!end! !!!!end !!end
20. before_validation after_validation before_save before_create after_create after_save after_commit
21. 8IBU
    DBO
    XF
    EP
    BCPVU
    JU
23. 0QUJPO
    
24. 3BJMT
    "DUJWF3FDPSE
    BOE
    UIFJS
    DPOWFOUJPOT
    BSF
    SVCCJTI
25. #FDBVTF
    {{your_favourite_OO_guru}}
    TBZT
    TP
27. :PV
    OFFE
    B
    4FSWJDF
    -BZFS
28. :PV
    OFFE
    %$*
29. :PV
    OFFE
    )FYBHPOBM
30. 0QUJPO
    
31. WARNING THE FOLLOWING SLIDE MAY BE FOUND DISTURBING BY SOME VIEWERS WARNING THE FOLLOWING SLIDE MAY BE FOUND DISTURBING BY SOME VIEWERS
32. I <3 Rails
33. $PODFSOT
34. 8IBU
    8IZ
    )PX
    8IBU
    FMTF
35. .JYJOT
36. module DogFort def call_dog puts "this is dog!" end end class Dog include DogFort end http://schneems.com/post/21380060358/concerned-about-code-reuse
37. ActiveSupport::Concern
38. module M extend ActiveSupport::Concern included do scope :disabled, where(:disabled => true) end module ClassMethods # class methods end # instance methods end http://api.rubyonrails.org/classes/ActiveSupport/Concern.html
39. class Article < ActiveRecord::Base include Taggable
40. module Taggable extend ActiveSupport::Concern included do has_many :taggings has_many :tags, through: :taggings scope :tagged_with, ->(tag_name) do joins(:tags).where(tags: { name: tag_name }) end end def tag_list tags.pluck(:name).join(', ') end def tag_list=(tag_list) assign_tag_list tag_list end private def assign_tag_list(tag_list) tag_names = tag_list.split(',').map(&:strip).uniq self.tags = tag_names.map do |tag_name| Tag.where(name: tag_name).first_or_initialize end end end
41. 8IBU
    8IZ
    )PX
    8IBU
    FMTF
42. 5IFZ
    IFMQ
    UP
    LFFQ
    DPIFTJPO
    IJHI XIFO
    VTFE
    QSPQFSMZ
43. module Taggable extend ActiveSupport::Concern included do has_many :taggings has_many :tags, through: :taggings scope :tagged_with, ->(tag_name) do joins(:tags).where(tags: { name: tag_name }) end end def tag_list tags.pluck(:name).join(', ') end def tag_list=(tag_list) assign_tag_list tag_list end private def assign_tag_list(tag_list) tag_names = tag_list.split(',').map(&:strip).uniq self.tags = tag_names.map do |tag_name| Tag.where(name: tag_name).first_or_initialize end end end
44. %3:OFTT
45. *OUSPEVDF
    MFTT
    JOEJSFDUJPO
    BOE
    DFSFNPOZ
    UIBO
    PUIFS
    BCTUSBDUJPOT DPNQPTJUJPO
    EFDPSBUJPO
46. l0⒏DJBM
    TPMVUJPOz
    UP
    UIF
    #JH
    .PEFMT
    JTTVF
    JO
    3BJMT
    
47. https://github.com/rails/rails/commit/f6bbc3f582bfc16da3acc152c702b04102fcab81
48. app/controllers/concerns app/models/concerns
49. 8IBU
    8IZ
    )PX
50. 8IBU
    8IZ
    OPU
    )PX
51. http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
52. http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/
53. https://twitter.com/hakunin/statuses/113364211727482880
54. Ruby Science The reference for writing fantastic Rails applications. https://learn.thoughtbot.com/products/13-ruby-science
55. .JYJO *OIFSJUBODF JT B DPNNPO NFUIPE PG SFVTF JO PCKFDUPSJFOUFE TPGUXBSF 3VCZ TVQQPSUT TJOHMF JOIFSJUBODF VTJOH TVCDMBTTFT BOE NVMUJQMF JOIFSJUBODF VTJOH NJYJOT .JYJOT DBO CF VTFE UP QBDLBHF DPNNPO IFMQFST PS QSPWJEF B DPNNPO QVCMJD JOUFSGBDF )PXFWFS NJYJOT IBWF TPNF ESBXCBDLT t 5IFZ VTF UIF TBNF OBNFTQBDF BT DMBTTFT UIFZSF NJYFE JOUP XIJDI DBO DBVTF OBNJOH DPOnJDUT t "MUIPVHI UIFZ IBWF BDDFTT UP JOTUBODF WBSJBCMFT GSPN DMBTTFT UIFZSF NJYFE JOUP NJYJOT DBOU FBTJMZ BDDFQU JOJUJBMJ[FS BSHVNFOUT TP UIFZ DBOU IBWF UIFJS PXO TUBUF t 5IFZ JOnBUF UIF OVNCFS PG NFUIPET BWBJMBCMF JO B DMBTT t 5IFZSF OPU FBTZ UP BEE BOE SFNPWF BU SVOUJNF https://learn.thoughtbot.com/products/13-ruby-science https://learn.thoughtbot.com/products/13-ruby-science
56. *OIFSJUBODF JT B DPNNPO NFUIPE PG SFVTF JO PCKFDUPSJFOUFE TPGUXBSF 3VCZ TVQQPSUT TJOHMF JOIFSJUBODF VTJOH TVCDMBTTFT BOE NVMUJQMF JOIFSJUBODF VTJOH NJYJOT .JYJOT DBO CF VTFE UP QBDLBHF DPNNPO IFMQFST PS QSPWJEF B DPNNPO QVCMJD JOUFSGBDF )PXFWFS NJYJOT IBWF TPNF ESBXCBDLT t 5IFZ VTF UIF TBNF OBNFTQBDF BT DMBTTFT UIFZSF NJYFE JOUP XIJDI DBO DBVTF OBNJOH DPOnJDUT t "MUIPVHI UIFZ IBWF BDDFTT UP JOTUBODF WBSJBCMFT GSPN DMBTTFT UIFZSF NJYFE JOUP NJYJOT DBOU FBTJMZ BDDFQU JOJUJBMJ[FS BSHVNFOUT TP UIFZ DBOU IBWF UIFJS PXO TUBUF t 5IFZ JOnBUF UIF OVNCFS PG NFUIPET BWBJMBCMF JO B DMBTT t 5IFZSF OPU FBTZ UP BEE BOE SFNPWF BU SVOUJNF t 5IFZSF EJʺDVMU UP UFTU JO JTPMBUJPO TJODF UIFZ DBOU CF JOTUBOUJBUFE 4ZNQUPNT https://learn.thoughtbot.com/products/13-ruby-science https://learn.thoughtbot.com/products/13-ruby-science
57. TVQQPSUT TJOHMF JOIFSJUBODF VTJOH TVCDMBTTFT BOE NVMUJQMF JOIFSJUBODF VTJOH NJYJOT .JYJOT DBO CF VTFE UP QBDLBHF DPNNPO IFMQFST PS QSPWJEF B DPNNPO QVCMJD JOUFSGBDF )PXFWFS NJYJOT IBWF TPNF ESBXCBDLT t 5IFZ VTF UIF TBNF OBNFTQBDF BT DMBTTFT UIFZSF NJYFE JOUP XIJDI DBO DBVTF OBNJOH DPOnJDUT t "MUIPVHI UIFZ IBWF BDDFTT UP JOTUBODF WBSJBCMFT GSPN DMBTTFT UIFZSF NJYFE JOUP NJYJOT DBOU FBTJMZ BDDFQU JOJUJBMJ[FS BSHVNFOUT TP UIFZ DBOU IBWF UIFJS PXO TUBUF t 5IFZ JOnBUF UIF OVNCFS PG NFUIPET BWBJMBCMF JO B DMBTT t 5IFZSF OPU FBTZ UP BEE BOE SFNPWF BU SVOUJNF t 5IFZSF EJʺDVMU UP UFTU JO JTPMBUJPO TJODF UIFZ DBOU CF JOTUBOUJBUFE 4ZNQUPNT t .FUIPET JO NJYJOT UIBU BDDFQU UIF TBNF QBSBNFUFST PWFS BOE PWFS https://learn.thoughtbot.com/products/13-ruby-science https://learn.thoughtbot.com/products/13-ruby-science
58. http://blog.8thlight.com/eric-meyer/2012/11/16/composition-over-mixins.html
59. http://blog.8thlight.com/eric-meyer/2012/11/16/composition-over-mixins.html
60. http://blog.8thlight.com/eric-meyer/2012/11/16/composition-over-mixins.html
61. http://blog.8thlight.com/eric-meyer/2012/11/16/composition-over-mixins.html
62. %PO`U
    pY
    QSPCMFN
    KVTU
    NPWF
    JU
63. %PO`U
    pY
    QSPCMFN
    KVTU
    NPWF
    JU .BOZ
    NFUIPETSFTQPOTJCJMJUJFT
64. %PO`U
    pY
    QSPCMFN
    KVTU
    NPWF
    JU .BOZ
    NFUIPETSFTQPOTJCJMJUJFT /BNJOH
    DPOqJDUT
65. %PO`U
    pY
    QSPCMFN
    KVTU
    NPWF
    JU .BOZ
    NFUIPETSFTQPOTJCJMJUJFT /BNJOH
    DPOqJDUT 4IBSFE
    TUBUF
66. %PO`U
    pY
    QSPCMFN
    KVTU
    NPWF
    JU .BOZ
    NFUIPETSFTQPOTJCJMJUJFT /BNJOH
    DPOqJDUT 4IBSFE
    TUBUF /P
    FYQMJDJU
    CPVOEBSJFT
67. http://37signals.com/svn/posts/3372-put-chubby-models-on-a-diet-with-concerns
68. http://37signals.com/svn/posts/3372-put-chubby-models-on-a-diet-with-concerns
69. +BWB 3VCZ /VNCFS
    PG
    NFUIPET
    JO
    4USJOH
    DMBTT
70. article.method(:tag_names).source_location # => ["./app/models/concerns/taggable.rb", 23]
71. &OPVHI
    SPQF
    UP
    IBOH
    PVSTFMWFT
72. 6TF
    WT
    "CVTF
73. 8IBU
    8IZ
    )PX
    8IBU
    FMTF
74. $PNNPO
    QVSQPTF
75. $PNNPO
    QVSQPTF /PU
    CBTJD
    OBUVSF
    PG
    NPEFM
76. $PNNPO
    QVSQPTF /PU
    CBTJD
    OBUVSF
    PG
    NPEFM $SPTTDVUUJOH
77. $PNNPO
    QVSQPTF /PU
    CBTJD
    OBUVSF
    PG
    NPEFM $SPTTDVUUJOH %PNBJO
    DPODFQU
78. # app/models/article.rb class Article < ActiveRecord::Base include Accessors include Validations include Associations include Scopes # ... end
79. # app/models/article.rb class Article < ActiveRecord::Base include Taggable include Searchable include Movable include Visible include Trashable # ... end
80. 8IBU
    8IZ
    )PX
    8IBU
    FMTF
81. (BUFXBZ
    PCKFDUT
82. http://slides.jcoglan.com/di-eurucamp#13 class Github::Client def initialize(http_client) @http = http_client end def get_user(name) data = @http.get("/users/#{name}").json_data Github::User.new(data) end end
83. http_client = HTTPClient.new('https://api.github.com') github = Github::Client.new(http_client) github.get_user(params[:name])
84. TwitterPoster.new(current_user, @comment.body).post FacebookPoster.new(current_user, @comment.body).post NotificationsMailer.new_comment(@comment).deliver
85. 3FTQPOTJCJMJUZ
    PCKFDUT
86. http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ class UserAuthenticator def initialize(user) @user = user end def authenticate(unencrypted_password) return false unless @user if BCrypt::Password.new(@user.password_digest) == unencrypted_password @user else false end end end
87. user = User.where(email: params[:email]).first UserAuthenticator.new(user).authenticate(params[:password])
88. https://gist.github.com/brynary/4670393 user!=!User.where(email:!params[:email]).first UserAuthenticator.new(user).authenticate(params[:password]) class!ActiveUserPolicy !!LOGIN_PERIOD!=!14.days !! !!def!initialize(user) !!!!@user!=!user !!end !!def!active? !!!!@user.email_confirmed?!&& !!!!@user.last_login_at!<!LOGIN_PERIOD.ago !!end !!class!Query !!!!def!initialize(relation!=!User.scoped) !!!!!!@relation!=!relation !!!!end !!!!def!find_each(&block) !!!!!!@relation. !!!!!!!!where(email_confirmed:!true). !!!!!!!!where('last_login!<!?',!LOGIN_PERIOD.ago). !!!!!!!!find_each(&block) !!!!end !!end end ActiveUserPolicy.active?(user)
89. ActiveUserPolicy.new(user).active? ActiveUserPolicy::Query.new(current_company.users).find_each do |user| # ... end
90. module User::Active extend ActiveSupport::Concern included do scope :active, -> do where(email_confirmed: true). where('last_login < ?', 14.days.ago) end end def active? user.email_confirmed? && user.last_login_at < 14.days.ago end end https://gist.github.com/cavalle/4660239
91. https://gist.github.com/brynary/4670393 user!=!User.where(email:!params[:email]).first UserAuthenticator.new(user).authenticate(params[:password]) class!ActiveUserPolicy !!LOGIN_PERIOD!=!14.days !! !!def!initialize(user) !!!!@user!=!user !!end !!def!active? !!!!@user.email_confirmed?!&& !!!!@user.last_login_at!<!LOGIN_PERIOD.ago !!end !!class!Query !!!!def!initialize(relation!=!User.scoped) !!!!!!@relation!=!relation !!!!end !!!!def!find_each(&block) !!!!!!@relation. !!!!!!!!where(email_confirmed:!true). !!!!!!!!where('last_login!<!?',!LOGIN_PERIOD.ago). !!!!!!!!find_each(&block) !!!!end !!end end ActiveUserPolicy.active?(user)
92. user.active? current_company.users.active.each do |user| # ... end
93. ActiveUserPolicy.active?(user) ActiveUserPolicy::Query.new(current_company.users).find_each do |user| # ... end
94. 3PMFT
95. class Commenter def initialize(person) @person = person end def recent_comments @person.comments.where("created_at > ?", 3.days.ago) end def post_comment(text) @person.comments.create(:body => text) end def update_comment(new_text) raise "Comment not owned by this person" unless comment.author == @person comment.update_attribute(:body, new_text) end end https://gist.github.com/4341122
96. *O
    TVNNBSZ
97. 8IBU
    8IZ
    )PX
    8IBU
    FMTF
98. 5IBOLT -VJTNJ
    $BWBMMÉ
    
    UXJUUFSDPNDBWBMMF
    HJUIVCDPNDBWBMMF
    QJOCPBSEJOVDBWBMMFUCJHNPEFMT