Mixin class methods

ruby-talk
1

Hello all,

I have another question regarding Mixins. How can I mix in class
methods?

I’d like the folling to work:

module Foo
def Foo.foo # this doesn’t work
return "foo"
end
end

class Bar
include Foo
end

Bar.foo # -> NameError: undefined method `foo’ for Bar:Class

Any help is appreciated!
-billy.

···

–
Meisterbohne Söflinger Straße 100 Tel: +49-731-399 499-0
eLösungen 89077 Ulm Fax: +49-731-399 499-9

2

Try “extend” (see below):

···

module A
def b(x)
print x, "\n"
end
end

class Foo
extend A
end

Foo.b(3) ==> “3”

Steve Tuckner
-----Original Message-----
From: Philipp Meier [mailto:meier@meisterbohne.de]
Sent: Wednesday, July 03, 2002 1:26 PM
To: ruby-talk@ruby-lang.org
Subject: Mixin class methods

Hello all,

I have another question regarding Mixins. How can I mix in class
methods?

I’d like the folling to work:

module Foo
def Foo.foo # this doesn’t work
return "foo"
end
end

class Bar
include Foo
end

Bar.foo # -> NameError: undefined method `foo’ for Bar:Class

Any help is appreciated!
-billy.

Meisterbohne Söflinger Straße 100 Tel: +49-731-399 499-0
eLösungen 89077 Ulm Fax: +49-731-399 499-9

3

Be forewarned that class variables used in A are A’s class variables,
and not Foo’s:

module A
def c=(x)
@@c = x
end

def c
  @@c
end

end

class Foo
extend A
end

Foo.c = 3
p Foo.c #=> 3

class Bar
extend A
end

p Bar.c #=> 3

I’ve been bitten by this before.

Paul

···

On Thu, Jul 04, 2002 at 03:35:20AM +0900, Steve Tuckner wrote:

Try “extend” (see below):

module A
def b(x)
print x, “\n”
end
end

class Foo
extend A
end

Foo.b(3) ==> “3”