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comp.lang.ruby

Re: Delegating class methods

Michael Malone

3/1/2009 8:58:00 PM

class Klass

extend Forwardable

def_delegators :@object :method1, :method2, :method3

def initialize
@object = SomeKlass.new
end

end
> Hi all,
>
> how would you forward calls from class methods to a class atribute?
> Like in:
>
> class Foo
> @@hash = {}
>
> def self.size
> @@hash.size
> end
> end
>
> I have to delegate a fairly large number of calls to an attribute. I'm
> currently using method_missing, but I was wondering if there was a
> cleaner way to do that as the method names are known at load time. I
> didn't find any using the standard library. Perhaps using some
> metaprogramming.
>
> Thanks!
>
>


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1 Answer

lasitha

3/2/2009 5:20:00 AM

0

On Mon, Mar 2, 2009 at 2:27 AM, Michael Malone
<michael.malone@tait.co.nz> wrote:
> On Mon, Mar 2, 2009 at 2:03 AM, abc <arcadiorubiogarcia@gmail.com> wrote:
>>
>> how would you forward calls from class methods to a class atribute?
>> [...]
>>
>> I have to delegate a fairly large number of calls to an attribute. [...]
>
> class Klass
> extend Forwardable
> def_delegators :@object :method1, :method2, :method3
>
> def initialize
> @object = SomeKlass.new
> end
> end

No, that would forward to an instance variable and only work with
Klass instances.

If the OP doesn't mind using a singleton class variable instead of a
class variable [1], then we can still use forwardable:

class Foo
@hash = {}
class << self
extend Forwardable
def_delegators :@hash, :[], :[]=, :size
end
end

Foo[:bar] = 'baz'
Foo.size #=> 1

Solidarity,
lasitha

[1] Generally a good idea anyway, right?