A simple ruby method to cleanup nested module setup for namespacing.

namespace.rb

def ns(namespace, delim = '.', &block)
  nest_mod(namespace.split(delim), block)
end

def nest_mod(mod = Kernel, module_names, block)
  return mod.module_exec(&block) if module_names.empty?
  find_or_create_constant_in_module(mod, constantize(module_names.first)).tap do |this|
    make_module_methods_accessible(this)
    this.module_exec do
      nest_mod(this, module_names.drop(1), block)
    end
  end
end

def make_module_methods_accessible(mod)
  mod.module_exec { extend self }
end

def find_or_create_constant_in_module(mod, str)
  return mod.const_get(str) if mod.const_defined?(str)
  return mod.const_set(str, Module.new)
end

def constantize(str)
  str.split('_')
     .map(&:capitalize)
     .join
end

if $0 !~ /rspec/
  ns 'my_app.greetings.greeter' do
    def present
      'hello'
    end
  end
  ns :presenters_greetings do
    def present_greeting(greeter)
      greeter.present
    end
  end
  puts Presenters::Greetings.present_greeting(MyApp::Greetings::Greeter) #=> 'hello'
else
  describe 'namespace' do
    context 'ns' do
      it 'creates all methods in the nested namespace/module' do
        ns 'my_app.dojo.util.options' do
          def names
            %w(john jill steve carol)
          end
        end
        expect(MyApp::Dojo::Util::Options.names).to eq(%w(john jill steve carol))
      end
      it 'custom deliminators can optionally be specified' do
        ns 'my_app|dojo|util|options', '|' do
          def names
            %w(john jill steve carol)
          end
        end
        expect(MyApp::Dojo::Util::Options.names).to eq(%w(john jill steve carol))
      end
    end
    context 'nest_mod' do
      it 'creates a module given a string and block' do
        nest_mod(['greeter'], Proc.new {
          @hello = 'hello'
          def greet
            @hello
          end
        })
        expect(Greeter.greet).to eq('hello')
      end
      it 'creates nested modules' do
        nest_mod(['dojo', 'util', 'options'], Proc.new {
          def names
            %w(john jill steve carol)
          end
        })
        expect(Dojo::Util::Options.names).to eq(%w(john jill steve carol))
      end
    end
    context 'to_const' do
      it 'hello_world -> HelloWorld' do
        expect(to_const('hello_world')).to eq('HelloWorld')
      end
    end
  end
end

usage.rb

module Presenters
  module Greetings
    def present_greeting(greeter)
      greeter.present
    end
  end
end

module MyApp
  module Greetings
    module Greeter
      def present
        'hello'
      end
    end
  end
end

#vs

ns 'presenters.greetings' do
  def present_greeting(greeter)
    greeter.present
  end
end

ns 'my_app.greetings.greeter' do
  def present
    'hello'
  end
end

I originally made this gist private on accident, if you're curious in some of the revisions the code went through, there is some more history in the private gist. https://gist.github.com/jah2488/a9d891d4393d2e5df327