From: "David A. Black" <dblack@...>
Date: 2009-07-29T19:46:40+09:00
Subject: Re: instance_eval

Hi --

On Wed, 29 Jul 2009, Abhishek Singh wrote:

> def method_missing(method_name,*args)
>  for @@y in(0..@@e-1) do
>    if ("#{method_name}"==@@a[0][@@y])
>      @@index=@@y
>      break
>      else if (@@y==@@e-1)
>      puts "This method (#{method_name})does not belong to any field
> value .. !!"
>        end
>   end
> end
>  instance_eval " def #{method_name}; puts '#{@@a[@@x][@@index]}'; end"
> end
>
> and when i want to access this newly defined method i'm doing
> following:-
>
> ro1=RecordOne.find("subject","algorithm")
> ro1.author
> ro1.author
>
> i'm not able to get value at single method call...:(

A typical pattern is to redefine the method and then call it using
send:

   class C
     def method_missing(m,*args,&block)
       instance_eval "def #{m}; puts 'In new method!'; end"
       send(m)
     end
   end

   C.new.blah   # In new method!

In your case that might look something like this (untested):

   def method_missing(method_name,*args)
     index = @@a[0].index(method_name)
     if index
       instance_eval <<-EOM
         def #{method_name}
           puts #{@@a[@@x][index]}
         end
       EOM
       send(method_name)
     else
       super
     end
   end

I don't know what all the class variables are for, and I've tried to
eliminate the ones that seem to be serving only as local variables.


David

-- 
David A. Black / Ruby Power and Light, LLC / http://www.rubypal.com
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