Is there any difference between Ruby class method calling with in class method with and without self?

Question

I am little bit curious about to know that, is there any difference between below two approaches?

1. Calling class method with in class method using self

   class Test
     def self.foo
      puts 'Welcome to ruby'
     end
   
    def self.bar
     self.foo
    end
   
   end
   

   Test.bar # Welcome to ruby

2. Calling class method with in class method without self

   class Test
     def self.foo
      puts 'Welcome to ruby'
     end
   
    def self.bar
     foo
    end
   
   end
   

   Test.bar # Welcome to ruby

Answer 1

Yes, there is a difference. But not in your example. But if foo was a private class method, then your first version would raise an exception, because you call foo with an explicit receiver:

class Test
  def self.foo
    puts 'Welcome to ruby'
  end
  private_class_method :foo

  def self.bar
    self.foo
  end
end

Test.bar
#=> NoMethodError: private method `foo' called for Test:Class

But the second version would still work:

class Test
  def self.foo
    puts 'Welcome to ruby'
  end
  private_class_method :foo

  def self.bar
    foo
  end
end

Test.bar
#=> "Welcome to ruby"