hacks/safe_mixin

class Module < Object

A hack that allows mixins to only be mixed in to classes that have the specified methods defined.

TODO: Is there any way to do this but still allow 'include' to occur at the top of the class definition?

TODO: One way to do this is to disallow instantiation of the object unless the specific methods are defined. This is how C++ does it; the advantage is that virtual functions in the base class can be implemented in anywhere in the hierarchy. A way around this for now is to declare a "stub" in the base class for any mixins that use mixin_requires, though this has its own set of problems.

E.g.:

  module Foo
    mixin_requires :foo, :bar
    def xyz
      # If foo and bar are not defined in the derived class, then this will
      # raise an exception, so it's best to know that this won't work at
      # load-time.
      foo
      bar
    end
  end
  class Bar
    def foo
      puts "foo"
    end
    def bar
      puts "bar"
    end
    # This must come last, because foo and bar must be defined before
    # including Foo.  If they are not defined, then an exception will be
    # thrown.
    include Foo
  end

Public Methods

mixin_requires(*methods)

Require that the class/module that a mixin is being included in MUST define certain methods.

methods	symbols representing the methods that MUST be defined.

Requires