Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
What the hell is ActiveSupport::Concern?
Search
Aaron Patterson
December 04, 2012
Programming
5
280
What the hell is ActiveSupport::Concern?
A short talk about ActiveSupport::Concern.
Aaron Patterson
December 04, 2012
Tweet
Share
More Decks by Aaron Patterson
See All by Aaron Patterson
RubyKaigi 2025: Class New, A New Approach
tenderlove
0
81
RubyKaigi Dev Meeting 2025
tenderlove
1
3.4k
Speeding up Instance Variables in Ruby 3.3
tenderlove
2
450
[Feature #20425] Speeding up delegate methods
tenderlove
3
280
RailsConf 2023
tenderlove
30
1.2k
Don't @ Me! Faster Instance Variables with Object Shapes
tenderlove
1
470
RailsConf 2022 Keynote
tenderlove
2
570
Some Assembly Required
tenderlove
1
580
HexDevs 2021
tenderlove
1
480
Other Decks in Programming
See All in Programming
【第4回】関東Kaggler会「Kaggleは執筆に役立つ」
mipypf
0
950
Kiroの仕様駆動開発から見えてきたAIコーディングとの正しい付き合い方
clshinji
1
180
ECS初心者の仲間 – TUIツール「e1s」の紹介
keidarcy
0
140
為你自己學 Python - 冷知識篇
eddie
1
310
『リコリス・リコイル』に学ぶ!! 〜キャリア戦略における計画的偶発性理論と変わる勇気の重要性〜
wanko_it
1
620
兎に角、コードレビュー
mitohato14
0
160
AIコーディングAgentとの向き合い方
eycjur
0
250
時間軸から考えるTerraformを使う理由と留意点
fufuhu
5
270
Improving my own Ruby thereafter
sisshiki1969
1
130
私の後悔をAWS DMSで解決した話
hiramax
4
170
MCPで実現するAIエージェント駆動のNext.jsアプリデバッグ手法
nyatinte
7
990
Nuances on Kubernetes - RubyConf Taiwan 2025
envek
0
220
Featured
See All Featured
We Have a Design System, Now What?
morganepeng
53
7.8k
Documentation Writing (for coders)
carmenintech
73
5k
Done Done
chrislema
185
16k
How to Think Like a Performance Engineer
csswizardry
26
1.8k
Connecting the Dots Between Site Speed, User Experience & Your Business [WebExpo 2025]
tammyeverts
8
500
How GitHub (no longer) Works
holman
315
140k
Making the Leap to Tech Lead
cromwellryan
134
9.5k
Responsive Adventures: Dirty Tricks From The Dark Corners of Front-End
smashingmag
252
21k
The Straight Up "How To Draw Better" Workshop
denniskardys
236
140k
Creating an realtime collaboration tool: Agile Flush - .NET Oxford
marcduiker
31
2.2k
Principles of Awesome APIs and How to Build Them.
keavy
126
17k
The Cult of Friendly URLs
andyhume
79
6.6k
Transcript
Thanks!
Hark
Substantial
What the hell is ActiveSupport::Concern?
I have no idea.
U Concerned, Bro?
Aaron Patterson @tenderlove
Lead Pun Architect
Substantial, Thanks
None
Gorbachev Puff-Puff Thunderhorse
None
None
None
None
None
None
Rails Core ~ 3 years (I think)
Confession
What’s in a name?
Classes ❤ File ❤ Hash ❤ Set ❤ Array
Modules ❤ Enumerable ❤ Comparable
AS::Concern
“Concern” is a noun
“Concern” is a noun
“Son, We’re Concerned”
Grown Man.
Stay Classy Change Your Self Track Dependents
Stay Classy.
Class Methods module MyEnumerable def my_first end module ClassMethods def
my_new end end def self.included(klass) klass.extend ClassMethods end end
Including class Aaron include MyEnumerable end p Aaron.respond_to?(:my_new) # =>
true p Aaron.new.respond_to?(:my_first) # => true
With Concern module MyEnumerable extend ActiveSupport::Concern def my_first end module
ClassMethods def my_new end end end
Including class Aaron include MyEnumerable end p Aaron.respond_to?(:my_new) # =>
true p Aaron.new.respond_to?(:my_first) # => true
Be Careful!
Normal Include module MyEnumerable def my_first end end class Aaron
p singleton_methods # => [] include MyEnumerable p singleton_methods # => [] end
Normal Extend module MyEnumerable def my_first end end class Aaron
p singleton_methods # => [] extend MyEnumerable p singleton_methods # => [:my_first] end
Users May Be Surprised
Do I need this?
Are you coupled?
Change Your Self.
Setting up ivars
Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def
self.included klass klass.extend ClassMethods end end
Warning! class Aaron include MyEnumerable p foo end
Warning! class Aaron include MyEnumerable p foo end @foo not
initialized
Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def
self.included klass klass.extend ClassMethods @foo = 10 end end
Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def
self.included klass klass.extend ClassMethods @foo = 10 end end self == MyEnumerable
Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def
self.included klass klass.extend ClassMethods klass.class_eval do @foo = 10 end end end
Working Code class Aaron include MyEnumerable p foo # =>
10 end
With Concern module MyEnumerable extend ActiveSupport::Concern module ClassMethods attr_accessor :foo
end included do @foo = 10 end end self == included class
Isolating Setup
Class Method Calls class Foo < ActiveRecord::Base scope :foo, ->
{ ... } scope :bar, -> { ... } scope :baz, -> { ... } # other methods end
Module Extraction module Findable def self.included(klass) klass.scope :foo, -> {
... } klass.scope :bar, -> { ... } klass.scope :baz, -> { ... } end end
Module Extraction module Findable def self.included(klass) klass.scope :foo, -> {
... } klass.scope :bar, -> { ... } klass.scope :baz, -> { ... } end end
class_eval module Findable def self.included(klass) klass.class_eval do scope :foo, ->
{ ... } scope :bar, -> { ... } scope :baz, -> { ... } end end end
Concerned module Findable extend ActiveSupport::Concern included do scope :foo, ->
{ ... } scope :bar, -> { ... } scope :baz, -> { ... } end end
Track Your Dependents.
Two Modules module Foo module ClassMethods def some_method end #
.... end end module Bar def self.included klass klass.some_method end end
Bar depends on Foo
Usage class Aaron include Foo include Bar end
Usage - BOOM! class Aaron include Bar include Foo end
Try to Fix module Foo module ClassMethods def some_method end
end end module Bar include Foo def self.included klass klass.some_method end end
Try to Fix module Foo module ClassMethods def some_method end
end end module Bar include Foo def self.included klass klass.some_method end end
Fix with class_eval module Bar def self.included klass klass.class_eval do
include Foo end klass.some_method end end
Concerned module Bar extend ActiveSupport::Concern include Foo included do some_method
end end
Concerned module Bar extend ActiveSupport::Concern include Foo included do some_method
end end NOT Ruby’s Include
When should I be concerned?
You probably shouldn’t be.
Can you simplify?
Many Dependencies
THANKS!