Ruby self Keyword Tutorial

In this section, we will learn what the self-keyword is and how to use it in Ruby.

What is self keyword in Ruby?

The `self` keyword is used within the body of instance methods and it represents the object that is invoking the target method.

We use self-keyword specially when there’s a local variable in a method and an instance variable or an instance method with the same name.

Basically, when there is a similarity between names in the body of a method, it’s hard for Ruby to differentiate between what’s what and we might get an error because of this confusion!

For example, let’s say you have a getter method name `first_name` and a local variable with the same name. Now within the body of the method that has such a local variable, let’s say we want to call the `first_name` method! How does Ruby know whether we’re calling a local variable or the method with the same name?!

This is where we can use the `self` keyword!

By prefixing the self-keyword to an instance method, Ruby knows that we want to call an instance method with the specified name which belongs to the current object that is calling the enclosing method.

Alright, it might seem a little confusing at first, but when we get into an example, you’ll see how easy it is the concept of the self-keyword.

Ruby self Keyword Syntax:


Using `self` keyword is within the body of an instance method. For example, if there’s a method named “get_name” and it belongs to an object named `emp`, we can use the `self` keyword within the body of that method. Now in this body, the self-keyword represents the `emp` object. This means if the object has another method like `get_lastname` for example, we can call `self.get_lastname` which is equal to `emp.get_lastname` and it will return the result of calling the `get_lastname` method.

Example: using the self keyword in Ruby

class Person 

    attr_accessor :first_name, :last_name, :id, :company

    def initialize(first_name, last_name, id, company = "Google")
        self.first_name = first_name
        self.last_name = last_name = id = company

prs ="John","Doe",500)

puts prs.first_name, prs.last_name,,

How does self keyword work in Ruby?

Note that within the body of the `initialize` method we have name collision! Basically, the name of parameters is equal to the name of the setter and getter methods in the `Person` class.

So in order to differentiate between the names of parameters and instance methods, we prefixed the names of instance methods with the `self` keyword to say these are the instance methods and not the parameters.

Again, the `self` keyword represents the object that invoked the enclosing method! So for this example, the `prs` object invoked the `initialize` method and so the `self` keyword is representing the `prs` object within the body of the initialize method.


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