How to automatically include a module in nested submodules

Question

I have a Top module that has modules A and B In each of them I want to use the class methods of the C module. To do this, I must include C for each module A and B Is it possible to include C in Top so that its class methods are accessible to all submodules?

Example:

 # I'll extend module C in example to make it shorter module C def foo; puts 'Foo!' end end module Top extend C module A end module B end end # That how it works now Top.foo #=> "Foo!" Top::A.foo #=> NoMethodError: undefined method `foo' for Top::A:Module Top::B.foo #=> NoMethodError: undefined method `foo' for Top::B:Module # That how I want it to work Top.foo #=> "Foo!" Top::A.foo #=> "Foo!" Top::B.foo #=> "Foo!" 

Answer 1

Well actually you can ... OP updated code, so here is my implementation:

 class Module def submodules constants.collect {|const_name| const_get(const_name)}.select {|const| const.class == Module} end end module C # this gets called when the module extends another class or module # luckily it does _not_ get called when we extend via :send def self.extended(base) # collect all submodules and extend them with self base.submodules.each{|m| m.send :extend, self } end def c1 puts "c1" end end module Top module A;end module B;end # extend needs to go at the end - otherwise Top doesnt know about its submodules extend C end Top.c1 # => "c1" Top::A.c1 # => "c1" Top::B.c1 # => "c1" 

Answer 2

There is no built-in way. You should implement it like this:

 class Module def extend_each_module m constants.each do |sym| const_get(sym).instance_eval{extend(m) if kind_of?(Module)} end end end module C def foo puts "Foo!" end end module Top module A; end module B; end extend C extend_each_module C end Top.foo # => Foo! Top::A.foo # => Foo! Top::B.foo # => Foo!