From: Ezra Zygmuntowicz <ezmobius@...>
Date: 2006-07-15T04:35:50+09:00
Subject: Re: Preferred monkeypatching technique


On Jul 14, 2006, at 12:29 PM, Tom Werner wrote:

> Logan Capaldo wrote:
>>
>> On Jul 14, 2006, at 1:34 PM, Eric Hodel wrote:
>>
>>> On Jul 14, 2006, at 10:24 AM, Tom Werner wrote:
>>>
>>>> Eric Hodel wrote:
>>>>> On Jul 13, 2006, at 5:04 PM, Tom Werner wrote:
>>>>>
>>>>>> Eric Hodel wrote:
>>>>>>> You just described subclasses:
>>>>>>
>>>>>> Well, the idea is that the 3rd party software is going to be  
>>>>>> using whatever classes it has always used, so just creating a  
>>>>>> subclass doesn't get me anywhere because the 3rd party app  
>>>>>> (i.e. Rails) doesn't give a hoot about my BigNozzleFiretruck.
>>>>>
>>>>> Can you give a concrete example where this takes place?
>>>>>
>>>>
>>>> My specific purpose is to write a plugin for Rails that adds an  
>>>> option to each form field helper (the ones that create <input>  
>>>> tags) that specifies an appropriate class (since CSS attribute  
>>>> selector support is lacking in IE). So I'm using code like this:
>>>>
>>>> module ActionView
>>>>  module Helpers
>>>>    module FormHelper
>>>>
>>>>      # text
>>>>      alias_method :__classless_text_field, :text_field
>>>>      def text_field(object_name, method, options = {})
>>>>        __classless_text_field(object_name, method, options.merge 
>>>> ({:class => (options[:class].to_s + ' text').strip}))
>>>>      end
>>>>
>>>>    end
>>>>  end
>>>> end
>>>
>>> module X
>>>   def does_something(*options)
>>>     p options
>>>   end
>>> end
>>>
>>> module Y
>>>   def does_something(*options)
>>>     super('x', *options)
>>>   end
>>> end
>>>
>>> class C
>>>   include X
>>>   include Y
>>> end
>>>
>>> C.new.does_something 'foo'
>>>
>>> --Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
>>> This implementation is HODEL-HASH-9600 compliant
>>>
>>> http://trackmap.robotcoop.com
>>>
>>>
>>>
>>
>> Rails does "funny" things. These helpers are usually used from  
>> within eruby templates e.g:
>>
>> <html>
>>   <%= text_field( ... ) %>
>> </html>
>>
>> Rails sets up the context in which the templates are executed.  
>> He'd have to go into the actual rails source to fix this. OTOH...
>>
>> Ok just as I thought, Rails is not this dumb <g>
>>
>> Tom just do
>>
>> def text_field(*args)
>>    orig_result = super
>>    # modify orig result
>> end
>>
>> in app/helpers/application_helper.rb
>>
>> Or if you want it in a per controller bias app/helpers/ 
>> <controller>_helper.rb
>>
>> No monkey-patching required
>>
>
> That's quite true, it does work wonderfully in  
> application_helper.rb. Though there's something nice about having  
> the functionality reside in a plugin, making it reusable in a nicer  
> fashion. Thanks for the reminder!
>
> Tom


Tom-

	If you want to do that methodology in a plugin its as easy as  
dropping this in the init.rb of a blank plugin:

ActionView::Base.class_eval do
    def text_field(*args)
      orig_result = super
      # modify orig result
    end
end

-Ezra