The Book of Ruby

Creating Classes at Runtime

So far, you have modified classes and created new objects from existing classes. But how would you go about creating a completely new class at runtime? Well, just as you can use const_get to access an existing class, you can use const_set to create a new class. Here’s an example of how to prompt the user for the name of a new class before creating that class, adding a method (myname) to it, creating an instance (x) of that class, and calling its myname method:

create_class.rb

puts("What shall we call this class? ") className = gets.strip().capitalize() Object.const_set(className,Class.new) puts("I'll give it a method called 'myname'" ) className = Object.const_get(className) className::module_eval{ define_method(:myname){ ...