[fpc-pascal]Interface-only units (was: shared libraries interface)

Full_Name memsom at post.interalpha.co.uk
Fri Aug 2 14:06:39 CEST 2002

Quoting Jonas Maebe <jonas at zeus.rug.ac.be>:

> On Fri, 2 Aug 2002, Full_Name wrote:
> > One other point.. surely the interface is there just for the
> > convenience of the developer - like a C header file.
> No, it's mainly to guarantee portability between different compiler
> versions. 

But the interface is still to be thought of as 'read only' ? Otherwise, it 
would be possible to alter the interface... not good for maintenance.

eg. consider the following...

unit whatever;



uses x, y, z;

  TSomeEnumType = (set1, set2, set3, set4);

  TMyClass = class
    function SomeFunction(x: TSomeEnumType): string;
    function SomeFunction2: TSomeEnumType;
    procedure SomeProcedure(x: TSomeEnumType);
    property X: TSomeEnumType read getX write setX; 


What would happen if I compiler this, gave it to people, and someone changed 
TSomeEnumType? For example to the following:

  TSomeEnumType = (setNone, set1, set2, set3, set4, set5, set6);

If I had written code internally well, hopefully not too much would break, but 
I still think this is dangerous. This is one reason why the DCU/TPU concept 
arrived in the first place.


"Computer games don't affect kids; I mean if Pac-Man affected us as kids, 
we'd all be running around in darkened rooms, munching magic pills and 
listening to repetitive electronic music." 
Kristian Wilson, 
Nintendo, Inc, 1989

Version: 3.12
GCS d? s+++:+ a- C++ UL+ P L++ E---- W- N+ o+ K- w 
O- M V PS PE-- Y PGP- t- 5-- X- R- tv+ b+ DI++ D+ 
G e++ h--- r+++ y+++ 

More information about the fpc-pascal mailing list