[fpc-pascal] Passing a CORBA interface as parameter

[Sven Barth]

Am 21.12.2019 um 16:12 schrieb Adriaan van Os:
> Sven Barth via fpc-pascal wrote:
>>
>> The important difference in this regard between COM and CORBA 
>> interfaces is that for CORBA interfaces the "guid" is a ShortString, 
>> not a TGUID. Thus the compiler allows to convert a CORBA interface to 
>> a ShortString. For TObject.GetInterface this works, because it has a 
>> overload for ShortString. ;) (this is document here: 
>> https://www.freepascal.org/docs-html/current/ref/refse47.html#x100-1220007.6 
>
>
> Thanks, I hadn't seen that. Yes, this solves the problem. And this 
> clarifies that the CORBA interface-identifying string doesn't need to 
> be in GUID form, it can be something as simple as [ 'IMyInterface' ].
>
> I will note that the interface-identifier comparison below (in 
> procedure TestInterfaceParameter) doesn't work without the explicit 
> typecast from interface-identifier to "shortstring". Apparently, that 
> typecast is implicit when passing an interface-identifier as actual 
> parameter to a "shortstring" formal parameter.
>
> type
>     InterfaceType                           = string[ 255];
>
> procedure TestInterfaceParameter
>       ( const theInterface            : InterfaceType);
>     begin
>       if theInterface = InterfaceType( ITestInterface1)
>         then writeln
>            ( 'theInterface = ITestInterface1')
>     end;
>
> begin
>   TestInterfaceParameter
>     ( ITestInterface1)
> end.
That is because the compiler only implements the *assignment* of an 
interface to a ShortString (or TGUID for COM interfaces), not the 
comparison.

Regards,
Sven