self is a keyword in ruby which means it is reserved by Ruby to serve a specific purpose and we cannot use it like regular variables (although you can override it, but you shouldn’t).

What is self in Ruby?

Behaviour of self depends on what context it is defined. self can represent instance of class or the class itself. Let’s understand through examples.

1. within method

In this case, self represents the current instance of the class. It will be different for different instances of the class and will not intervene any proceedings between them.

Example 1:

class RailsExamples
  def method1
    self.__id__
  end
end

irb(main):1:0> obj = RailsExamples.new
irb(main):2:0> obj.method1
irb(main):3:0> 460060
irb(main):4:0> 
irb(main):5:0> obj.__id__
irb(main):6:0> 460060
irb(main):7:0> 
irb(main):8:0> obj.method1 == RailsExamples.new.method1
irb(main):9:0> false

2. Within class

In this case self will represent the class itself. It will return the Class object under which it is defined. Let’s understand through example -

Example 2:

class RailsExamples
  def method1
    self.__id__
  end

  def self.method2
    self.__id__
  end
end

irb(main):1:0> RailsExamples.method2
=> 992600
irb(main):2:0> RailsExamples.method2
=> 992600
irb(main):3:0> RailsExamples.__id__
=> 992600
irb(main):4:0> RailsExamples.new.method1.__id__
=> 2052721

3. Outside any context

When self is called outside any class or method, it refers the main object (the top-level context).

irb(main):218:0> p self
main
=> main

Happy Coding!!!

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References -

• keywords in Ruby