Types, Classes, and Modules in Ruby

Types, Classes, and Modules in Ruby

Class is nothing but a blueprint of objects in an object programming language. An object is also known as an instance of a class. The most widely used methods are those for identifying the type of objects, which means what Class it is an instance of and in which methods it responds. Types of classes present in ruby are as follows:

Defining Classes and Modules

We can create Classes and Modules dynamically. Classes and modules are instances of the Class and Module classes. We will create classes and modules dynamically below:

M = Module.new      # Define a new module M 
C = Class.new       # Define a new class C 
D = Class.new(C) {  # Define a subclass of C  include M         # that includes module M 
} 
D.to_s              # => "D": class gets the constant name by magic

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One great feature of Ruby programming language is that when we assign a constant to a dynamically created anonymous Module or Class, the name of that constant is used as the name of the Module or Class.

Modules in ruby

Modules are a collection of methods, constants, and class variables. The thing to keep in mind about modules is that we cannot inherit modules, or we cant create a subclass of a module. Also, All the classes are modules, but all the modules are not classes.

Syntax:

module Module_name
   . . . code
end

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Example:

module Ninja
    C = 7;
    
    # Prefix with name of Module
    # module method 
    def Ninja.portal
        puts "Welcome to Coding Ninjas Portal!"
    end
        
    # Prefix with the name of Module
    # module method
    def Ninja.tutorial  
        puts "Ruby Tutorial!"
    end
        
    # Prefix with the name of Module
    # module method
    def Ninja.topic  
        puts "Topic - modules in ruby"
    end
      
end
   
# displaying the value of 
# module constant
puts Ninja::C
  
# calling the methods of the module
Ninja.portal
Ninja.tutorial
Ninja.topic

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Output:

7
Welcome to Coding Ninjas Portal!
Ruby Tutorial!
Topic - modules in ruby

Ancestry and Modules

In addition to the above methods, there are few related reflective methods to determining the ancestors of a class or module and for determining which modules are included by a class or module. These methods are easy to understand when demonstrated:

module X; end # Empty module 
module Y; include X; end; # Module Y includes X 
class Z; include Y; end; # Class Z includes module Y

Z < Y # => true: Z includes Y
Y < X # => true: Y includes X 
Z < X # => true 
Fixnum < Integer # => true: all fixnums are integers
Integer < comparable # => true: integers are comparable
Integer < Fixnum # => false: not all integers are fixnums
String < Numeric # => nil: strings are not numbers

X.ancestors # => [X] 
B.ancestors # => [B, X] 
Z.ancestors # => [Z, Y, X, Object, Kernel] 

String.ancestors # => [String, Enumerable, Comparable, Object, Kernel] 
    # Note: Ruby 1.9 String is no longer Enumerable
Z.include?(B) # => true
Z.include?(X) # => true
Y.include?(X) # => true
X.include?(X) # => false
X.include?(B) # => false

X.included_modules # => []
Y.included_modules # => [X]
Z.included_modules # => [Y, X, Kernel]

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Frequently Asked Questions

What is a module and Class in Ruby?

Modules are collections of constants and methods; they cannot generate instances. while Class may generate instances or objects and also have instance variables.

Can a module include a module Ruby?

Yes, a module can be included in the other modules or classes; we have to just use some keywords such as include, prepend and extend.

What is the difference between an object and a class in Ruby?

The difference between an object and a class is that an object is a unit of data while a class is what kind of data it is.

What is class self in Ruby?

A class self method in ruby is a method that refers only to that Class in all contexts but not to any individual objects of that class.

What is the difference between modules and methods?

The method is a function that is related to an object or class, while a module is a group of defined functions, classes, constants, etc.

Conclusion

In this article, we discussed Reflection and Metaprogramming, types, classes, and modules in ruby. We started with the introduction of Reflection and Metaprogramming, and then we have seen types, classes, and modules in ruby with the help of some examples.

Here are more articles to the rescue:

• Introduction to Ruby
• Ruby from Coding Ninjas
• Everything you wished you knew about Ruby on Rails
• Ruby Official Documentation
• Ruby FAQ
• RubyKoans
   

If you want to learn more on such topics, you can see  Introduction to ruby on rails, Directory Structure in Ruby, Ruby on Rails, and Ruby vs. Python. You can explore some more articles on For Loop in Ruby, Operators in Ruby, or directly access the Coding Ninjas Studio for our courses.

You can also refer to our guided path on Coding Ninjas Studio to upskill yourself in Data structure and algorithms, Competitive Programming, Javascript, and System Design. Do upvote our blogs if you find them helpful and engaging!

Happy learning!