"is" operator equivalent for interfaces?

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2 total messages Started by masonwheeler Mon, 21 Jul 2008 16:05

#220

Author: masonwheeler
Date: Mon, 21 Jul 2008 16:05

12 lines
1588 bytes

I'm trying to make sure that any object passed to the write parameter
of a property implements a certain interface.  The obvious way for
checking inheritance, the "is" operator, doesn't seem to work. Is
there a different way to do it?

procedure TEngineData.setEngine(const Value: TEngine);
begin
   assert(value is IEngine); //compiler doesn't like this
   FEngine := Value;
end;

Any help would be appreciated.

Re: "is" operator equivalent for interfaces?

#222

Author: BRoberts
Date: Fri, 01 Aug 2008 00:32

19 lines
1993 bytes

<masonwheeler@gmail.com> wrote in message 
news:bf992d9f-7587-4aca-95f7-3d71cdad88e5@t12g2000prg.googlegroups.com...
> I'm trying to make sure that any object passed to the write parameter
> of a property implements a certain interface.  The obvious way for
> checking inheritance, the "is" operator, doesn't seem to work. Is
> there a different way to do it?
>
> procedure TEngineData.setEngine(const Value: TEngine);
> begin
>   assert(value is IEngine); //compiler doesn't like this
>   FEngine := Value;
> end;
>
> Any help would be appreciated.


Interfaces can be bound dynamically at runtime. You can wrap an assignment 
using the AS operator in a try except and trap the error at runtime. Can you 
not simply use an iEngine parameter?

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