From: Robert Klemme <shortcutter@...>
Date: 2008-10-20T17:33:11+09:00
Subject: Re: Proc metaprogramming tricks?

2008/10/19 Adam Skobi <dxm997@gmail.com>:
>
>> class C
>>    def self.inherited(klass)
>>      klass_name = klass.name[/[^:]+$/]
>>      klass.to_s.split(/::/)[0...-1].inject(Object) { |const, name|
>>        const.const_get name
>>      }.send :remove_const, klass_name
>>      C.const_set klass_name, klass
>>    end
>> end
>
>> NB: Don't do this.
>
> Yes! Why haven't I thought of this solution?!
> Thanks for that one.
>
> Are the any non obvious reasons as why not to do this type of trick
> (code obfuscation, maintance hell etc.)?

Yes, there's a reason: it does not work:

10:17:43 Temp$ ruby mod.rb
initial
A::X
A::X
after remove
A::X
A::X
after set
A::X
A::X
10:17:51 Temp$ cat mod.rb
module A
  class X
  end
end
$cl = ::A::X
puts "initial", $cl, $cl.name
A.send :remove_const, 'X'
puts "after remove", $cl, $cl.name
module B
end
B.send :const_set, 'Y', $cl
puts "after set", $cl, $cl.name
10:18:08 Temp$

Here's one way to do it:

class Root
  # features all objects of dsl share
  class Object
    def my_name
      # silly example
      self.class.name
    end
  end

  class <<self
    def class_def(name, parent = Object, &b)
      parent = const_get(parent) unless Module === parent
      cl = Class.new parent
      const_set name, cl
      cl.class_eval(&b)
      cl
    end
  end
end

def Object.const_missing(sym)
  Root.send :const_get, sym
end

def dsl(&b)
  Root.class_eval(&b)
end

dsl {
  class_def :Base do
    def hello() puts "Hello, I am #{my_name}." end
  end

  class_def :Derived, Base do
    # nothing here
  end

  Derived.new.hello

  p Derived.ancestors
}


Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end