From: dblack@...
Date: 2006-03-12T13:01:43+09:00
Subject: Re: Adding methods to a singleton dynamically

Hi --

On Sun, 12 Mar 2006, Mike Austin wrote:

> I'm building a view hierarchy from a file, and I would like it to add getter 
> methods for every subview created.  For example, I should be able to write:
>
> window.bottom_panel.save_button.left = 20
>
> I played around with singleton classes and define_method, am I close?  I 
> wonder if it is illegal to do 'class << self end' within a method - I get the 
> error 'class definition in method body'
>
> hierarchy.each do |key, value|
>  view = Object::const_get( key[1] ).new
>
>  class << self end

I get a syntax error on that; I think you need a semi-colon after
'self'.  However, even with the semi-colon, the expression doesn't do
anything.  (It just opens a class definition block and then closes
it.)  Do you want to capture the singleton class?  If so, you would
do:

   singleton_class = (class << self; self; end)

Inside the block, 'self' is the class itself.  (And vote for your
local RCR 231 :-)

>  self.class.class_eval do
>    define_method( key[1] ) do
>      return view
>    end
>  end
> end
>
> hierarchy = {
>  [:bottom_panel, :Panel] => {
>    [:save_button, :Button] => {}
>  }
> }

Does that last bit actually come first?

I haven't quite grasped what you want to do (due to tiredness, I
think), but maybe the above will help.


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

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