class and initialize method in Ruby

Class in Ruby

Ruby is a perfect Object Oriented Programming Language. The features of the object-oriented programming language include −

• Data Encapsulation
• Data Abstraction
• Polymorphism
• Inheritance

Objects are the products of the class. An object is an individual “thing”, with its own identity & its own data.

Example: A Book class could be the blueprint for creating books. This class defines what attributes ALL books have in common, like: title, author, pages

Code Example:

class  Book
    attr_accessor  :title, :author, :pages
end

Creating Objects using the “new” method in Ruby:

Classes and objects are the most important part of Ruby. Like class objects are also easy to create, we can create a number of objects from a single class. In Ruby, objects are created by the new method.

Syntax:

object_name = Class_name.new

book1 = Book.new()
book2 = Book.new()
book3 = Book.new()

Important Note:

• Class names start with an uppercase letter
• We use the class keyword, then the end keyword
• An empty class is not very useful, but you can still create objects from it

In above code example, book1 is an object of Book class. Every individual book is an object & we can make many of them thanks to the Book class.

Let’s initialize some value in book1:

book1.title = "Harry Potter"
book1.author = "JK Rowling"
book1.pages = 400

book1.title = "Lord of the rings"
book1.author = "Tolkien"
book1.pages = 500

puts book1.title
puts book2.author

Run the above codes:

Outputs:
Harry Potter
Tolkien

Passing Parameters to new Method:

User can pass any numbers of parameters to “new method” which are used to initialize the class variables. While passing parameters to “new method” it is must to declare an initialize method at the time of class creation. The initialize method is a specific method, which executes when the new method is called with parameters.

Code Example:

class  Book
    attr_accessor  :title, :author, :pages
    def initialize(title, author, pages)
        @title = title
        @author = author
        @pages = pages
    end
end

book1 = Book.new("Harry Potter", "JK Rowling", 400)
book2 = Book.new("Lord of the Ring", "Tolkein", 500)

puts book1.title
puts book2.author

Run the above codes:

Outputs:
Harry Potter
Tolkien

Explanations:

Here Book is the class name. def is a keyword which is used to define “initialize” method in Ruby. It is called whenever a new object is created. Whenever new class method called it always call initialize instance method. initialize method is like a constructor, whenever new objects are created initialize method called. title, author, pages, are the parameters in initialize method and @title @author, @pages are the local variables in initialize method with the help of these local variables we passed the value along the new method. The parameters in “new” method is always enclosed in double quotes.

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