Question

What is the difference between

module MyModule
  module MySubModule
    class MySubModuleClass
      ...
    end
  end
end

and

module MyModule
  class MySubModule::MySubModuleClass
    ...
  end
end

in Ruby?

Answer 1

the second case will not work unless “MySubModule” is already defined elsewhere…

the second case is not a proper definition of “MySubModule” and will cause an error if you didn’t define that MySubModule elsewhere

NameError: uninitialized constant MyModule::MySubModule
    from (irb):2:in `<module:MyModule>'