Dumb DI container

di.rb

class DIContainer
  def configure
    yield self
  end

  def method_missing(key, val)
    if key =~ /=$/
      key = key.to_s.chop
      (class << self; self; end).class_eval do
        attr_accessor key
      end
    
      __send__(:"#{key}=", val)
    else
      super
    end
  end
end

def configure
  Container.new.tap do |c|
    yield c
    
    c.freeze if freeze
  end
end

module A
  extend self
  
  def shout(foo: DI.foo)
    foo.shout
  end
end

module Foo
  extend self
  
  def shout;"the real foo";end
end

module FakeFoo
  extend self
  
  def shout;"fake foo!";end
end

DI = configure do |c|
  c.foo = Foo
end

A.shout

DI.configure do |c|
  c.foo = FakeFoo
end

A.shout