Re: How to handle this OOP/inheritance problem?

"Jim Leonard" <MobyGamer@[EMAIL PROTECTED]
> wrote in message
news:4e25725a-3fd4-4523-bc02-87a9e720485e@[EMAIL PROTECTED]
> But my question is:  How can I initialize my TPlayer object to call
> the right output device object?  Is the proper way to pass the pointer
> to the output device object to TPlayer during TPlayer's
> initialization?

You could use a registry of TOutputDevices that the TPlayer uses to obtain
the correct one, based on the file-extension of the song data, or the
TPlayer's own type - rather like one might obtain the correct bitmapped
image handler from the file-extension (*.bmp, *.jpg, etc). This would be a
one-time operation for each TPlayer and outside the "Play" loop, so does
not
need to be ultra-fast.

>  If so, what would the pointer type be?  Would it be
> the TOutputDevice abstract/ancestor's type, or the descendant's type?

You define an abstract TOutputDevice for two reasons:

(1) As a basis for creating non-abstract devices.
(2) As a means to define the interface to all TOutputDevice types.

So the device is passed as the abstract TOutputDevice type, but it will in
reality ALWAYS be a non-abstract descendant, because abstract objects are
never instantiated.

function TDeviceRegistry.GetDeviceFor(X: TSomeSpecifier): TOutputDevice;

> If my target platform were something other than an 8088, I would
> virtualize everything to within an inch of its life :-) but instead I
> have to balance form with function.

Virtualization doesn't have to cost you very much time at all - if you get
the design right.

-- 
Jay

Jason Burgon - author of Graphic Vision
http://homepage.ntlworld.com/gvision