From: Logan Capaldo <logancapaldo@...>
Date: 2006-04-03T05:44:43+09:00
Subject: Re: Dynamic code generation


On Apr 1, 2006, at 11:15 PM, Thiago Arrais wrote:

> On 4/1/06, Logan Capaldo <logancapaldo@gmail.com> wrote:
>> I don;t see what you  gain by meta-programming here
>
> I need a method to identify the child classes, something like
> Class#name, just more detailed. All instances of subclasses of the
> parent class need to respond to that method, but the method returns
> the same thing for all instances: a class identifier. Most classes
> will respond in mostly the same way, but some will need customization.
>
> Maybe a (almost) real example will help:
>
> ----
> class Parent
>
>     def identifier
>         return "This is class #{self.class.name}"
>     end
>
> end
>
> class ChildUsingDefaultIdentifier; end
>
> class ChildUsingCustomIdentifier
>
>     def identifier
>         return 'Instances of this class identify them on a totally
> different way'
>     end
>
> end
> ----
>
> Sure we could just override the method in the subclasses that needed
> to override it (like we did above), but it is just an identifier and a
> whole def block seemed too much.
>
> Regards,
>
> Thiago Arrais
>

This seems like a job for class constants:

% cat identifiers.rb
class A
   ID = "Class A"
end

class B < A # uses default id
end

class C < A # uses a custom id
ID = "Class C"
end

puts A::ID
puts B::ID
puts C::ID
puts A::ID

% ruby identifiers.rb
Class A
Class A
Class C
Class A