Ruby Self

The keyword self in ruby gives you access to the current object

Class

In the context of a class self refers to the current class

class Dog
  p self # the Dog class
end

Defining a method on self creates a class method

Instance Method

Within an instance method self refers to the instance itself

class Dog
  def bark
    self
  end
end

p Dog.new.bark # an instance of the Dog class

Implicit Self
When you call a method without an explicit recieving object, the method is called implicitely on self. In plain english this means that if there is nothing on the left hand side of the function call then the left hand side is self.

class Person
  attr_reader :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end

  def full_name
    "#{first_name} #{last_name}" #implied self. Instance of person
  end
end

Top Level

At the top level self refers to the main ruby object

p self # the main object

Modules

When self is used within an instance method of a module it refers to the instance of the class in which the module is included

When you see self outside of an instance method inside a module it refers to the module

If you were wondering what p by itself is. Its a kernel method that behaves similar to obj.inspect. Try calling it on some objects :)