From: Robert Klemme <shortcutter@...>
Date: 2006-11-19T06:10:12+09:00
Subject: Re: How to call a class method via the singleton if it exists

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On 18.11.2006 18:16, Robert Klemme wrote:
>> thanks robert. you helped clarify that unfortunately I've i mis-stated
>> the problem, there's a contradiction in my example, what I actually
>> meant was:
>>
>>    class X
>>      def self.f ; "A" ; end
>>      def g ; self.class.f ; end
>>    end
>>
>>    x = X.new
>>    x.g  #=> "A"
>>
>>    # this should be:
>>    class << x
>>      def self.f; "B"; end
>>    end
>>
>>    x.g  #=> "A"  # want "B"
>>
>> so #respond_to? won't help b/c I didn't intend #f to be instance level
>> method. sorry. what i'm asking for, should make a whole lot more sense
>> now (i hope)
>>
>> thanks,
>> T.
> 
> 
> Just replace self.class with class<<self;self;end in my code.
> 
>     robert
> 
How about this?

	robert


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#!/usr/bin/ruby

class Object
  # option 1
  def dispatch(m,*a,&b)
    [class <<self; self; end, self.class].find {|x| x.respond_to? m}.
      send(m,*a,&b)
  end

  # option 2
  class Dispatcher
    def initialize(*a) @a=a end
    def method_missing(m,*a,&b)
      @a.each {|o| return o.send(m,*a,&b) if o.respond_to? m}
      super
    end
  end

  def disp; Dispatcher.new(class <<self; self; end, self.class) end
end

  class X
    def self.f ; "A" ; end
    def g ; self.class.f ; end
    def h ; dispatch :f ; end
    def i ; disp.f ; end
  end

  x = X.new
p  x.g  #=> "A"
p  x.h  #=> "A"
p  x.i  #=> "A"

   class << x
     def self.f; "B"; end
   end

p  x.g  #=> "A"
p  x.h  #=> "B"
p  x.i  #=> "B"



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