Class methods in a module?

Ruby
1

At Scotland On Rails a few months ago, I was shown a nice way to put
class methods in a module, alongside instance methods, in such a way as
they will get added as class methods automatically, without any work
required on the part of the person including the module.

Unfortunately i failed to make a note of how to do this and i’ve since
forgotten. Can anyone show me?

It was something along these lines…(the following doesn’t work btw)

module Mappable

#instance methods
def foo
“foo”
end

#class methods
class << self.class
def bar
“bar”
end
end

end

can anyone set me straight?
thanks
max

2

2009/5/25 Max W. [email protected]

At Scotland On Rails a few months ago, I was shown a nice way to put
class methods in a module, alongside instance methods, in such a way as
they will get added as class methods automatically, without any work
required on the part of the person including the module.

Unfortunately i failed to make a note of how to do this and i’ve since
forgotten. Can anyone show me?

I’m not sure if you can pick up the singleton methods from the module
and
automatically copy them to the class – I’ve got type errors before when
trying to move and rebind methods. I did come up with this, though,
which is
more expressive than writing an included() hook on every module:

3

On Mon, May 25, 2009 at 11:07 AM, Max W.
[email protected] wrote:

module Mappable
end
end

end

can anyone set me straight?
thanks
max

The usual way is to use the hook method Module#included, something like:

module Mappable

#instance methods
def foo
“foo”
end

#class methods
module ClassMethods
def bar
“bar”
end
end

def self.included(other)
other.extend(ClassMethods)
end
end

By the way this nesting of a Module inside a module is another variant
on something discussed in another recent ruby-talk thread.

Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Twitter: http://twitter.com/RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
LinkedIn: http://www.linkedin.com/in/rickdenatale

4

Max W. wrote:

At Scotland On Rails a few months ago, I was shown a nice way to put
class methods in a module, alongside instance methods, in such a way as
they will get added as class methods automatically, without any work
required on the part of the person including the module.

Unfortunately i failed to make a note of how to do this and i’ve since
forgotten. Can anyone show me?

It was something along these lines…(the following doesn’t work btw)

module Stuff
module ClassMethods
def biff(*args)
# …
end

 def baz(*args)
   # ...
 end

end

def self.included(base)
base.extend(ClassMethods)
end

end

The methods defined in Stuff::ClassMethods are added as class methods
when

include Stuff

is called

–
James B.

www.jamesbritt.com - Playing with Better Toys
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