Ruby | Constructors (original) (raw)

Last Updated : 24 Feb, 2023

A constructor is a special method of the class that gets automatically invoked whenever an instance of the class is created. Like methods, a constructor may also contain a group of instructions or a method that will execute at the time of object creation.

Important points to remember about Constructors:

Constructors are used to initializing the instance variables.
In Ruby, the constructor has a different name, unlike other programming languages.
A constructor is defined using the initialize and def keywords.
It is treated as a special method in Ruby.
Constructors can't be overloaded in Ruby.
Constructors can't be inherited.
It returns the instance of that class.

Note: Whenever an object of the class is created using new method, internally it calls the initialize method on the new object. Also, all the arguments passed to new will automatically pass to method initialize.

Syntax:

class Class_Name

def initialize(parameter_list)

end

Example:

Ruby `

A Ruby program to demonstrate

the working of constructor

#!/usr/bin/ruby

class name

class Demo

# constructor
def initialize
    puts "Welcome to GeeksforGeeks!"
end

end

Creating Object

Demo.new

Output:

Welcome to GeeksforGeeks!

Initializing instance variable: Instance variables can be initialized using constructor. Inside the constructor, the initial value to instance variables is provided which can be used further anywhere in the program.