From: Sharon Phillips <phillipsds@...>
Date: 2007-11-28T18:28:37+09:00
Subject: define_method and instance variable maddness

Hi,

This problem has been driving me nuts, so I've finally given in and  
decided to ask for help.

I'm just cutting my teeth on metaprogramming but am stuck referencing  
instance variables within define_method

Here's the code snippet in question. It works, but is extremely ugly  
with its constant usage of instance_variable_get and set.

child_list_name= ('@'+(child.to_s)+"_list")
self_method= (self.name.downcase+'=').to_sym
method_name= ('add_'+child.to_s).to_sym

define_method method_name do |new_child|
   instance_variable_set(child_list_name, []) if  
instance_variable_get(child_list_name).nil?
   unless instance_variable_get(child_list_name).include? new_child
     instance_variable_set(child_list_name,  
(instance_variable_get(child_list_name) << new_child))
     if new_child.respond_to? self_method
       new_child.send self_method, self
     end
   end
end


This is what I'd really like the new method to look like (for  
child== :personnel):

def add_personnel (new_personnel)
   unless (@personnel_list||=[]).include? new_personnel
     @personnel_list << new_personnel
     self_method= (self.name.downcase+'=').to_sym
     if new_personnel.respond_to? self_method
       new_personnel.send self_method, self
     end
   end
end


Any help appreciated.

Cheers,
Dave