From: "Marcin Mielżyński" <lopx@...>
Date: 2007-05-12T02:10:12+09:00
Subject: Re: Creating and adding new methods in runtime

konryd wrote:
> Hello, I need to add in runtime several methods to my class. How can I
> accomplish this in ruby?
> More precisely: I need my class to overload arithmetic operators with
> fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
> stored in a hash, so I created a method to do all the stuff. It looks
> like do_operation(operator, other)
> But still I have to add every single operator overloader:
> class Fixnum
> 
>   def doo_operation(operator, other)
>   #...nevermind...
>   end
> 
>   def +(other)
>     do_operation(:+, other)
>   end
>   def -(other)
>     do_operation(:-, other)
>   end
> end
> 
> can I automate it somehow?
> 

the simplest case someone might come up with is:

module Operators

     def operation operator, other
         puts "operator #{operator} with argument #{other} called"
     end

     OPERATORS = [:+,:-,:/,:*]

     def self.included mod
         mod.instance_eval do
             OPERATORS.each do |op|
                 begin
                     instance_method(op)
                     alias_method(:"_#{op}", op)
                 rescue
                     # swallow NameError here
                 end

                 define_method op do |other|
                     # here you might want to check for 'other' class to 
preserve Numeric/Enumerable behaviour
                     operation op, other
                 end
             end
         end
     end

end

class Fixnum
     include Operators
end

1 + 2
1.send :"_+" ,2  # original

class A
     include Operators
end

A.new + A.new


lopex