[fpc-devel] A suggestion about streams

[Sergei Gorelkin]

On Friday, June 30, 2006, 6:46:48 PM, Michael Van Canneyt wrote:

MVC> There is a difference for the implementor of streams:
MVC> By keeping the method abstract, you FORCE the implementation of a method
MVC> in a descendent.

MVC> The compiler will warn you if you try to instantiate a class which has an
MVC> abstract method. If you implement the base method as virtual method, you
MVC> will lose this warning, but you will not be aware that you have forgotten
MVC> to override a method.

This is, of course, right. But is it important in particular case
of TStream? Stream implementors basically have to implement only 3-4
methods, so it's rather hard to forget to override a method. And even if
one does forget, that will pop out on the first run.

The majority of FCL streams (encrypting, compressing, buffering, pipes,
etc) are unidirectional, and only few (handle/file and memory) allow
both reading and writing. Calling an invalid method (e.g. Read for
write-only stream) is typically a programmer's (not user's) error and
should never happen in a well written program. For this reason, IMO,
keeping a separate handler and error message for each unidirectional
stream merely increases the program size.

-- 
Best regards,
 Sergei