Can an inner class get its container at runtime?

ruby-talk
1

Is there a way for an inner class to find out what class owns it? The
code I’d like to use looks like:

class AbstractInnerClass
def do_something
# here’s where I need to find the owner of the concrete child
end
end

class OuterClass
class ConcreteInnerClass < AbstractInnerClass
end
end

I’d love to be able to call ConcreteInnerClass#do_something and know
that it can find OuterClass. Is there a way for me to do this?

Francis

2

Maybe like this?

class AIC
def my_container_class
Object.const_get self.class.to_s.split(/::/)[0…-1].join(“::”)
end
end
==>nil
class Out
class In < AIC
end
end
==>nil
Out::In.new.my_container_class
==>Out

This will give an error if there is no outer class, but you should be
able to wrap the core code line in a begin…rescue block and/or check
the string to ensure non-emptyness before calling Object.const_get with
it.

HTH,
Mark

···

On May 28, 2004, at 1:33 PM, Francis Hwang wrote:

Is there a way for an inner class to find out what class owns it? The
code I’d like to use looks like:

class AbstractInnerClass
def do_something
# here’s where I need to find the owner of the concrete child
end
end

class OuterClass
class ConcreteInnerClass < AbstractInnerClass
end
end

I’d love to be able to call ConcreteInnerClass#do_something and know
that it can find OuterClass. Is there a way for me to do this?

3

Works like a charm, thanks! Ah, Ruby reflection.

Francis

Mark Hubbart <discord@mac.com> wrote in message news:<09241422-B0F3-11D8-8419-000502FDD5CC@mac.com>...

···

On May 28, 2004, at 1:33 PM, Francis Hwang wrote:

> Is there a way for an inner class to find out what class owns it? The
> code I'd like to use looks like:
>
> class AbstractInnerClass
> def do_something
> # here's where I need to find the owner of the concrete child
> end
> end
>
> class OuterClass
> class ConcreteInnerClass < AbstractInnerClass
> end
> end
>
> I'd love to be able to call ConcreteInnerClass#do_something and know
> that it can find OuterClass. Is there a way for me to do this?

Maybe like this?

   class AIC
     def my_container_class
       Object.const_get self.class.to_s.split(/::/)[0...-1].join("::")
     end
   end
     ==>nil
   class Out
     class In < AIC
     end
   end
     ==>nil
   Out::In.new.my_container_class
     ==>Out

This will give an error if there is no outer class, but you should be
able to wrap the core code line in a begin...rescue block and/or check
the string to ensure non-emptyness before calling Object.const_get with
it.

HTH,
Mark