IMyIntf = interface
  function GetValue: Variant;
end;

TMyObject=(TList, IMyIntf)
....
end;

Can not compile becuase it need to add this functions to TMyObject

         function QueryInterface(const iid : tguid;out obj) : longint;stdcall;
         function _AddRef : longint;stdcall;
         function _Release : longint;stdcall;

While i am not inherit IMyIntf from IUnknown or IInterface, Is there a way to not add unnecessary functions (for me at least).

Sorry for my bad English, and Thanks in advance.

All interfaces inherit from IUnknown, unless you use corba interfaces:
{$INTERFACES CORBA}

Michael.

Michael Van Canneyt wrote

{$INTERFACES CORBA}

{$INTERFACES CORBA}

It is resolved my problem, Is there any limit to use it (except it is not work in Delphi)?

Thank for your replay.

Not that I know of :-)

Michael.

You cannot use casts like
var
   a: IMyObject;
   b: IMyOtherObject;
begin
   b := a as IMyOtherObject;

or functions like supports() (which uses queryinterface)

Marc

Marc Weustink het geskryf:

I remember reading something about this a year or two ago in the mailing list. As far as I remember, there was an alternative to do the same thing with CORBA-style interfaces, but for the life of me I can't remember what it was. I'll keeps searching to see if I can find the answers I am referring to.

While searching I did find one of my old message threads. And the answers to the questions I asked then, still elude me [4 years later]. :-(

http://lists.freepascal.org/lists/fpc-devel/2007-November/012060.html

@Michael van Canneyt
Maybe the Language Reference documentation could be extended to include such information? And maybe address the issues I mentioned the the message thread link I posted. Many developers seem to struggle with this, and the documentation seems the right place to address such info.

Regards,
- Graeme -

You are right. I will have a look at the docus.

Michael.

Marc Weustink het geskryf:

or functions like supports() (which uses queryinterface)

Actually, that *does* work with FPC 2.4.0. See attached console application.

I used supports() and a cast to get a Corba interface reference. It seems the compiler does some extra magic (probably with the GUID) to identify the interface via the Supports() call - without the need for QueryInterface.

begin
 ins := TAddCommand.Create;
 if Supports(ins, ICommand, cmd) then
 begin
   writeln('1. It worked');
   cmd.Execute;               // works
 end;
 cmd := nil;
 cmd := ins as ICommand;
 if Assigned(cmd) then
 begin
   writeln('2. It worked');
   cmd.Execute;                // works
 end;
 ins.Free;
end.

....and the the output generated...

1. It worked
TAddCommand.Execute
2. It worked
TAddCommand.Execute

Regards,
- Graeme -

Extending the example program a but further to test for not supported interfaces I found that the cast (via as syntax) to get a interface gives a compiler error [test 3 it program]. Using supports() still worked though [test 4 in program].

Cheers,
- Graeme -

Can we have in the future something like IMyObject = interface(IObject) instead of use {$INTERFACES CORBA}