From: Joel VanderWerf <vjoel@...>
Date: 2002-12-10T06:26:07+09:00
Subject: Re: Newbie: invoking class methods

James Davis wrote:
> (Using Ruby 1.6.6)
> I am writing a game.  A "splash" screen displays four buttons to the
> user.  Each button has an action assigned to it, loaded from a file.
> When a user clicks a button, I want to execute a class method such as
> Game.new.  First, I thought I wanted a Proc for this purpose,  so I
> tried:
>    ba = proc {ba}  # ba = "Game.new"
> ....
>    ba.call
> This approach didn't work.  Didn't produce errors.  So I switched to
>   eval(ba)
> which does work, but I was hoping for a better technique.  Eval seems
> crude and unsafe to me, particularly since the button actions are
> loaded from a file.  I am wondering if there might be another approach
> such as something like "instance_method" for class methods, or send,
> or yield.  Any advice appreciated.  Thanks,

This is one way of limiting what actions the file can do:

   module GameModule
     class Game
       def self.new
         super
       end
     end
   end

   cmd = "Game.new"
   klass_str, meth = cmd.split(/\./)

   unless GameModule.constants.include? klass_str
     raise "Unrecognized class #{klass_str}"
   end
   klass = GameModule.const_get(klass_str)

   unless klass.singleton_methods.include? meth
     raise "Unrecognized method #{meth} for class #{klass}"
   end

   p klass.send(meth)