Module define_method

define_method(symbol) { block } => proc

Defines an instance method in the receiver. The method parameter can be a Proc or Method object. If a block is specified, it is used as the method body. This block is evaluated using instance_eval, a point that is tricky to demonstrate because define_method is private. (This is why we resort to the send hack in this example.)

   class A
     def fred
       puts "In Fred"
     end
     def create_method(name, &block)
       self.class.send(:define_method, name, &block)
     end
     define_method(:wilma) { puts "Charge it!" }
   end
   class B < A
     define_method(:barney, instance_method(:fred))
   end
   a = B.new
   a.barney
   a.wilma
   a.create_method(:betty) { p self }
   a.betty

produces:

   In Fred
   Charge it!
   #<B:0x401b39e8>