[fpc-pascal] Empty record inside another record ?

[Skybuck Flying]

There is another major drawback to your supposedly better method:

Object inheritance forces all fields to be accessable from the root:

SomeRoot.SomeField := ...;

While nesting has nice grouping:

SomeRoot.SomeHeader.SomeOtherHeader.SomeField := 5;

Bye,
  Skybuck.


----- Original Message ----- 
From: "Daniël Mantione" <daniel.mantione at freepascal.org>
To: "FPC-Pascal users discussions" <fpc-pascal at lists.freepascal.org>
Sent: Saturday, February 16, 2008 5:24 PM
Subject: Re: [fpc-pascal] Empty record inside another record ?




Op Fri, 15 Feb 2008, schreef Skybuck Flying:

> To me it seems like some kind of trick, to extend a record at runtime.
>
> The empty record field, functions as a sort of offset/label/pointer if you
> will to the new fields that will will be extended to the record by simply
> allocating more memory then the size of the record.
>
> Then this "label"/"field" can be used as a sort of offset, by typecasting 
> it
> to some extension record type.
>
> Could be pretty handy, quite impressive trick.
>
> However, is it safe to use ?

Empty records are valid Pascal.

> I cannot find anything in the documentation about this ?

Nothing in the documentation says it is forbidden either. The reason
it is not explicetely mentioned is because there exists a
much better method, objects:

type  base_structure=object
         field1:byte;
       end;

       extended_structure=object(base_structure)
         field2:byte;
       end;

Daniël


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