class vs Class.new, module vs Module.new

Question

What is difference between class and Class.new & module and Module.new?

I know that:

1. C

Answer 1

The interesting point that you missed between class keyword and Class::new is - Class::new accepts block. So when you will be creating a class object using Class::new you can also access to the surrounding variables. Because block is closure. But this is not possible, when you will be creating a class using the keyword class. Because class creates a brand new scope which has no knowledge about the outside world. Let me give you some examples.

Here I am creating a class using keyword class :

count = 2

class Foo
    puts count
end
# undefined local variable or method `count' for Foo:Class (NameError)

Here one using Class.new :

count = 2
Foo = Class.new do |c|
    puts count
end
# >> 2

The same difference goes with keyword module and Module::new.