Ruby - Module Mix-Ins

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Introduction

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.

For example:

Demo

module UsefulFeatures 
  def class_name 
    self.class.to_s 
  end #  w  w  w  . j a  v a 2  s  . co m
end 

class Person 
  include UsefulFeatures 
end 

x = Person.new 
puts x.class_name

Result

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:

Demo

module AnotherModule 
  def do_stuff # from   w  w w .  j  ava2 s.c  o  m
    puts "This is a test" 
  end 
end 

include AnotherModule 
do_stuff

Result

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: 

AnotherModule.do_stuff

include takes a module and includes its contents into the current scope.

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