Why is `yield self` helpful?

Question

As a Ruby newbie, it's confusing to me why it would ever be beneficial to yield self within a method definition. I've come across this functionality in a number of tutorials as being something that is helpful -- it makes perfect sense to me how this works, but I don't understand why you'd ever use it.

Let's say I have the following code:

class Dog

  attr_accessor :breed

  def initialize
    @breed = "Westie"
  end

  def bark
    puts "Woof!"
    yield self if block_given?
  end

end

fido = Dog.new

fido.bark do |d|
  puts "Bark, bark, bark!"
  puts d.breed  
end

So yeah, via yield self, I now have access to the instance of the Dog class within the block that I am yielding too.

But, even if I don't yield self, I would still have access to that instance, right? In other words, wouldn't the code below work exactly the same as the code above?

class Dog

  attr_accessor :breed

  def initialize
    @breed = "Westie"
  end

  def bark
    puts "Woof!"
    yield
  end

end

fido = Dog.new

fido.bark do
  puts "Bark, bark, bark!"
  puts fido.breed   
end

Note that in the second code sample, I'm not calling yield self.

I'm clearly missing the utility here.

Answer 1

The second example works because of the specific circumstances where you have a local variable referring to the the Dog. As an alternative consider what happens if using an anonymous instance:

Dog.new.bark do
  puts "Bark, bark, bark!"
  # what goes here?? puts ????.breed   
end

or maybe you want to declare your block somewhere else and pass it in e.g.

loud = lambda { |dog| puts "A #{dog.breed} doing some LOUD YAPPING" }

puts d.bark(&loud)

so essentially setting up with yield self gives flexibility in how your code can be used.