Ruby Class vs Module

21 Mar 2014 Tags: | ruby

Ruby modules allow you to create groups of methods that you can then include or mix into any number of classes. Modules only hold behaviour, unlike classes, which hold both behaviour and state.

Since a module cannot be instantiated, there is no way for its methods to be called directly. Instead, it should be included in another class, which makes its methods available for use in instances of that class.

Here are the quick pointers of exact difference between a class and module.

	Class	Module
instantiation	can be instantiated	can not be instantiated
usage	object creation	mixin facility, provide a name space.
super class	module	object
consists of	methods, constants and variables	methods, constants and classes
methods	class methods, instance methods	module methods, instance methods
inheritance	inherits behaviour and can be base for inheritance	No inheritance
inclusion	cannot be included	can be included in classes and modules by using the include command (includes all instance methods as instance methods in class/module)
extension	cannot be extend with extends	module can extend instance by using extend command (extends given instance with singleton methods from module)

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Thanks for reading!