From: Chris Czub <chris.czub@...>
Date: 2007-10-26T04:42:01+09:00
Subject: Re: Need help understanding metaclassing

Daniel Waite wrote:
> Daniel Waite wrote:
>> cs.instance_eval do
>>   define_method(:eat) do
>>     puts "You eat."
>>   end
>> end
>> 
>> cs.eat # => errors:
>> NoMethodError: undefined method `eat' for 
>> #<Class:#<Creature:0xb7f78ae8>>
>> 
>> Why is that? I've tried class_eval, too and I get the same thing. I 
>> thought I understood this stuff pretty well but I guess not.
> 
> This works:
> 
> cs.instance_eval do
>   def eat
>     puts "You eat."
>   end
> end
> 
> cs.eat # You eat.
> 
> What's up with define_method?

The method is put into the Creature class and is inaccessible in the 
simpleton class.

Try this:

class Creature

  def singleton
    class << self
      self
    end
  end

end

c = Creature.new
cs = c.singleton

cs.instance_eval do
  define_method(:eat) do
    puts "You eat."
  end
end

c.eat
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