Question

What is happening in the following code

A = Class.new

class << A
  def speak
    puts "Dave"
  end
end

A.speak
B = A.new 

How is this possible what is really happening. and what is ‘Class’ class.

Answer 1

A = Class.new

This is similar to:

class A
end

As you are defining an empty class and giving it the name A. (NB: In Ruby the convention is that identifiers starting with a capital letter are constants.)

class << A
  def speak
    puts "Dave"
  end
end

is similar to:

class A
  def A.speak
    puts "Dave"
  end
end

Here you are defining a class method on A (as opposed to an instance method).

The line:

A.speak

is simply calling the class method.

Finally:

B = A.new

is creating an instance of class A and assigning it to the constant B.

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To answer your other question. The class of Class is… Class! You can see this in irb:

irb(main):022:0> Class.class
=> Class