=begin
it's quite common, in ruby, for modules to provide functionality via mixins.
for example:
=end
module Mixin
def foo
42
end
end
class C
include Mixin
end
p C.new.foo #=> 42
=begin
althouge handy, the guts of the mixin, especially modules, can easily leak
into the target unintentially.
here the 'Util' module gets zippered in-between the Mixin and C:
=end
reset!
module Mixin
module Util
def Util.foo
42
end
end
end
class C
include Mixin
p Util.foo #=> 42
module Util
def Util.bar
42.0
end
end
p Util.bar #=> 42.0
end
=begin
this creates a challenge for the author's of mixins: how to keep code
organized *and* provide a module that is safe to mixin to any target.
two main approaches exist:
1) carve out the mixin seperately from the top-level namespace
=end
reset!
module M
module Mixin
def foo
42
end
end
module Util
end
end
class C
include M::Mixin
end
p C.new.foo #=> 42
p C.const_defined?(:Util) #=> false
=begin
or
2) leverage const_missing to allow simple const aliases into a private namespace
=end
reset!
module M
module Namespace
module Util
def foo
42
end
end
end
def Mixin.const_missing(const)
begin
Namespace.const_get(const)
rescue Object
raise
end
end
def foo
Util.foo
end
end
class C
include M::Mixin
end
p C.new.foo #=> 42
p C.const_defined?(:Util) #=> false
=begin
so, there you have it: please think carefully about dropping common names
inside your mixins as they absolute vommit all their internals into the
mixee.
=end
BEGIN {
def reset!
self.class.send :remove_const, :Mixin rescue false
self.class.send :remove_const, :C rescue false
end
}