This document discusses issues with using the Data Context Interaction (DCI) pattern in Ruby. It provides examples of implementing DCI by extending classes with modules versus using delegation. Performance benchmarks show extending classes is slower due to Ruby's method cache being invalidated. Delegation is presented as an alternative that avoids this performance penalty. The document concludes by inviting questions about these DCI implementation approaches in Ruby.

1. Ruby and DCI
You’re doing it wrong
Simon Courtois - @happynoff

2. DCI ?
Data (domain model)
Context
Interaction (roles)

3. Example
d::Base
< A ctiveRecor
class User e}")
def tweet _name My nam e is #{nam
.se nd_tweet("
TwitterLib
end
end
user = User.find(42)
user.tweet_name

4. Example
cor d::Base
< ActiveRe
class User
end
module TwitterUser
def tweet_name
TwitterLib.send_tweet("M
y name is #{name}")
end
end
user = User.find(42)
user.extend(TwitterUser)
user.tweet_name

5. Performance ?
http://tonyarcieri.com/dci-in-ruby-is-completely-broken
Tony Arcieri
@bascule

6. Performance ?
Benchmark.ips do |bm|
bm.report("without dci") { ExampleClass.new.foo }
bm.report("with dci") do
obj = ExampleClass.new
obj.extend(ExampleMixin)
obj.foo
end
end
Local - Ok
Global - What ?!

7. Ruby’s cache
Ruby VMs cache methods
« These caches remain valid so long
as we don’t see new types and the
class hierarchy doesn’t change. »
Tony Arceria

8. Alternative
cor d::Base
< ActiveRe
class User
Evan Light
end
class TwitterUser < Simp
leDelegator
def tweet_name
TwitterLib.send_tweet("M
y name is #{name}")
end
end
user = User.find(42)
tw_user = TwitterUser.new(user)
tw_user.tweet_name

9. Questions ?
Simon Courtois - @happynoff

10. Thanks !
Simon Courtois - @happynoff