Ruby | Module (original) (raw)

Last Updated : 10 Oct, 2018

A Module is a collection of methods, constants, and class variables. Modules are defined as a class, but with the module keyword not with class keyword. Important Points about Modules:

• You cannot inherit modules or you can't create a subclass of a module.
• Objects cannot be created from a module.
• Modules are used as namespaces and as mixins.
• All the classes are modules, but all the modules are not classes.
• The class can use namespaces, but they cannot use mixins like modules.
• The name of a module must start with a capital letter.

Syntax:

module Module_name

statements to be executed

end

Example:

Ruby `

Ruby program to illustrate

the module

Creating a module with name Gfg

module Gfg

C = 10;

# Prefix with name of Module
# module method 
def Gfg.portal
    puts "Welcome to GFG Portal!"
end
  
# Prefix with the name of Module
# module method
def Gfg.tutorial  
    puts "Ruby Tutorial!"
end
  
# Prefix with the name of Module
# module method
def Gfg.topic  
    puts "Topic - Module"
end

end

displaying the value of

module constant

puts Gfg::C

calling the methods of the module

Gfg.portal Gfg.tutorial Gfg.topic

`

Output:

10 Welcome to GFG Portal! Ruby Tutorial! Topic - Module

Note:

• To define module method user have to prefix the name of the module with the method name while defining the method. The benefit of defining module method is that user can call this method by simply using the name of module and dot operator as shown in above example.
• A user can access the value of a module constant by using the double colon operator(::) as shown in the above example.
• If the user will define a method with def keyword only inside a module i.e. def method_name then it will consider as an instance method. A user cannot access instance method directly with the use of the dot operator as he cannot make the instance of the module.
• To access the instance method defined inside the module, the user has to include the module inside a class and then use the class instance to access that method. Below example illustrate this concept clearly.
• The user can use the module inside the class by using include keyword. In this case, the module works like a namespace.

Example:

Ruby `

Ruby program to illustrate how

to use module inside a class

Creating a module with name Gfg

module Gfg

# module method 
def portal
    puts "Welcome to GFG Portal!" 
end
 
# module method
def tutorial  
    puts "Ruby Tutorial!" 
end
 
# module method
def topic  
    puts "Topic - Module" 
end

end

Create class

class GeeksforGeeks

# Include module in class
# by using 'include' keyword
include Gfg
 
# Method of the class
def add
    x = 30 + 20
    puts x
end

end

Creating objects of class

obj_class = GeeksforGeeks.new

calling module methods

with the help of GeeksforGeeks

class object

obj_class.portal obj_class.tutorial obj_class.topic

Calling class method

obj_class.add

`

Output:

Welcome to GFG Portal! Ruby Tutorial! Topic - Module 50

Use of Modules: A module is a way categorize the methods and constants so that user can reuse them. Suppose he wants to write two methods and also want to use these methods in multiple programs. So, he will write these methods in a module, so that he can easily call this module in any program with the help of require keyword without re-writing code.Example:

Ruby `

Ruby program for creating a module

define module

module Gfg

# module method 
def Gfg.portal()
    
    puts "Module Method 1"  
end

# module method 
def Gfg.tutorial()
    
    puts "Module Method 2"  
end

end

`

Note: Save this program in a file named as my.rb. You can use this into another program with the help of require keyword. This is like including the header files in C/C++ program.Using Command:

ruby my.rb

Now create a another file containing the following code:

Ruby `

Ruby program to show how to use a

module using require keyword

adding module

require "./my.rb"

calling the methods of module Gfg

Gfg.portal() Gfg.tutorial()

`

Save this file as my1.rb.Using Command:

ruby my1.rb

Output:

Module Method 1 Module Method 2