The document discusses ActiveSupport::Concern, a module in Ruby on Rails that provides a way to write reusable modules. It handles dependencies between modules and includes common functionality like scopes. ActiveSupport also allows pluggable JSON backends for improved performance and includes helper methods like presence that simplify checking for blank values. Classes can also define inheritable class attributes using ClassAttribute.

1. ACTIVESUPPORT
Sunday, September 12, 2010

2. WHOAMI
Sunday, September 12, 2010

3. HOW WE WRITE MODULES
Sunday, September 12, 2010

4. module M
def self.included(base)
base.extend, ClassMethods
base.send(:include, InstanceMethods)
scope :disabled, where(:disabled => true)
end
module ClassMethods
...
end
module InstanceMethods
...
end
end
Sunday, September 12, 2010

5. previously wrote
HOW WE WRITE MODULES
Sunday, September 12, 2010

6. ACTIVESUPPORT::CONCERN
Sunday, September 12, 2010

7. module M
extend ActiveSupport::Concern
included do
scope :disabled, where(:disabled => true)
end
module ClassMethods
...
end
module InstanceMethods
...
end
end
Sunday, September 12, 2010

8. Why use it?
Sunday, September 12, 2010

9. ...it handles dependencies to other
modules!
Sunday, September 12, 2010

10. module Bar
extend ActiveSupport::Concern
include Foo
included do
self.method_injected_by_foo
end
end
class Host
include Bar
end
Sunday, September 12, 2010

11. ActiveSupport::Concern in the Wild
Sunday, September 12, 2010

12. module Mongoid #:nodoc
module Indexes #:nodoc
extend ActiveSupport::Concern
included do
cattr_accessor :index_options
self.index_options = {}
end
module ClassMethods #:nodoc
# Send the actual index creation comments to the MongoDB driver
def create_indexes
return unless index_options
current_collection = self._collection || set_collection
index_options.each do |name, options|
current_collection.create_index(name, options)
end
end
...
end
end
end
Sunday, September 12, 2010

13. PLUGGABLE JSON BACKENDS
Sunday, September 12, 2010

14. #to_json calls ActiveSupport::JSON.encode()
Sunday, September 12, 2010

15. Rails used to only have YAML-based JSON support
Sunday, September 12, 2010

16. ActiveSupport::JSON.backend = 'Yajl'
Sunday, September 12, 2010

17. YAJL BENCHMARKS
Yajl::Encoder#encode: 3.59s
JSON#to_json: 6.2s
ActiveSupport::JSON.encode: 45.58s
Yajl::Parser#parse: 4.54s
JSON.parse: 5.47s
ActiveSupport::JSON.decode: 64.42s
Sunday, September 12, 2010

18. PRESENCE
Sunday, September 12, 2010

19. BEFORE
name = params[:name] unless params[:name].blank?
Sunday, September 12, 2010

20. NOW
name = params[:name] if params[: name].present?
Sunday, September 12, 2010

21. BEFORE
state = params[:state] unless params[:state].blank?
country = params[:country] unless params[:country].blank?
region = state || country || 'US'
Sunday, September 12, 2010

22. NOW
region = params[:state].presence || params[:country].presence || 'US'
Sunday, September 12, 2010

23. ARRAY#UNIQ_BY
Sunday, September 12, 2010

24. [1, 2, 3, 4].uniq_by(&:odd?)
#=> [1, 2]
Sunday, September 12, 2010

25. CLASS_ATTRIBUTE
Sunday, September 12, 2010

26. Declare one or more class-level attribute
whose value is inheritable and over-writable by
subclasses and instances
Sunday, September 12, 2010

27. >> Base.setting = "foo" => "foo"
>> Subclass.setting => "foo"
>> Subclass.setting = "bar" => "bar"
>> Base.setting => "foo"
Sunday, September 12, 2010

28. QUESTIONS?
Sunday, September 12, 2010