From: Mike Papper <bodarotech@...>
Date: 2009-12-08T06:26:33+09:00
Subject: Re: Use of extend <module> from within a Class

Thanks for the clarification and sample.

So, I cannot simply extend the ActionController::UrlWriter module in my 
class because that module does this:

self.class.default_url_options.merge(options)

However, within a rails controller, this module can be included as a 
"helper". Does anyone know how the magic rails helper function makes 
this call to self.class.default_url work? I've looked at the code for 
helper but cannot really make any sense of it.

Mike

...
> The normal pattern is
> 
> module SomeModule
>    # define any instance methods here
> 
>    module ClassMethods
>        # define any class methods here
>    end
> 
>   # and here is the crucial step  this gets called when some class
>   # includes the module
>   def self.included(some_class)
>      some_class.extend(ClassMethods)
>   end
> end
> 
> So if you want to make a module which adds only class methods either
> 
> 1) define the module 'normally' and in the class which wants the
> methods as class methods
> 
>      class Foo
>          extend MyGreatModuleOfClassMethods
>      end
> 
> or
> 
>  2) Use the pattern above, leave the instance methods out, and put all
> of the methods in the inner ClassMethods module (actually the name of
> this module is irrelevant except for clarity. then in the using class
> 
>      class Foo
>          include MyGreatModuleWhichOnlyHasClassMethodsRightNow
>      end
> 
> HTH
> 
> 
> 
> 
> --
> Rick DeNatale
> 
> Blog: http://talklikeaduck.denhaven2.com/
> Twitter: http://twitter.com/RickDeNatale
> WWR: http://www.workingwithrails.com/person/9021-rick-denatale
> LinkedIn: http://www.linkedin.com/in/rickdenatale

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