Ruby doesn't support multiple inheritance.
One class cannot inherit from multiple classes at the same time.
To share functionality between disparate classes, you can use modules.
Modules act like a sort of "super" class and can be included into other classes, extending that class with the methods the module offers.
module UsefulFeatures def class_name self.class.to_s end # from w w w .j ava 2s . c o m end class Person include UsefulFeatures end x = Person.new puts x.class_name
Here, UsefulFeatures looks almost like a class.
Modules are organizational tools rather than classes.
The class_name method exists within the module, and is then included into the Person class.
Here's another example:
module AnotherModule def do_stuff # ww w . j a v a2s . c o m puts "This is a test" end end include AnotherModule do_stuff
Here, you can include module methods in the current scope, even if you're not directly within a class.
It is like a class and you can use the methods directly:
include takes a module and includes its contents into the current scope.