Question

In Ruby, is there a difference between writing class Foo::Bar and module Foo; class Bar for namespacing? If so, what?

Answer 1

If you use class Foo::Bar, but the Foo module hasn’t been defined yet, an exception will be raised, whereas the module Foo; class Bar method will define Foo if it hasn’t been defined yet.

Also, with the block format, you could define multiple classes within:

module Foo
  class Bar; end
  class Baz; end
end