Hi,
I tested the attached program under Delphi 7 and FPC 2.6.0 and FPC 2.7.1
(dated 2012-11-15).
The test application tests two things:
1) Interface delegation via another class
2) Overriding a interface implementation using method resolution
Under Delphi 7 the test application compiles and runs as expected.
Under FPC (both 2.6.0 and 2.7.1)
- I get a compiler error. I thought interface delegation was
supported in FPC?
- I also get a compiler crash with an AV - in both versions.
Isn't interface delegation supported in FPC?
Is method resolution supported in FPC?
Why does the compiler crash while compiling?
----8<-------------8<-------------8<-------------8<-------------8<----
Free Pascal Compiler version 2.6.0 [2011/12/23] for x86_64
Copyright (c) 1993-2011 by Florian Klaempfl and others
Target OS: Linux for x86-64
Compiling test.pas
test.pas(38,76) Error: Class "TMyIntfClass" does not implement interface
"IMyIntf"
Fatal: Compilation aborted
An unhandled exception occurred at $000000000054CA3D :
EAccessViolation : Access violation
$000000000054CA3D
$0000000000532148
$000000000056CEF4
$000000000042392F
----8<-------------8<-------------8<-------------8<-------------8<----
The expected output when running the test application should be:
----------------------------------------------------------
c:\Programming\test\interface_delegation_2>test
TMyIntfClass.P1
TMainForm.MyP2
----------------------------------------------------------
Regards,
- Graeme -
--
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
http://fpgui.sourceforge.net/
program test;
{$ifdef FPC}
{$mode objfpc}{$H+}
{$else}
{$APPTYPE CONSOLE}
{$endif}
uses
Classes;
//-------------- Interface ------------------
type
IMyIntf = interface(IInterface)
['{ED858BD2-0E49-4B42-861D-6F415A7C0CF0}']
procedure P1;
procedure P2;
end;
{ Delegation class.
NOTE: Documenatation suggested we use the TAggregatedObject, but
under Delphi 7 (at least) we can use TObject too. }
TMyIntfClass = class(TObject)
private
{ IMyIntf implementation }
procedure P1;
procedure P2;
end;
TMainForm = class(TComponent, IMyIntf)
private
FMyIntfClass: TMyIntfClass;
{ delegate IMyIntf implementation to another class }
property MyIntfClass: TMyIntfClass read FMyIntfClass implements IMyIntf;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure Run;
{ overrides the IMyIntf.P2 implementation using name resolution }
procedure IMyIntf.P2 = MyP2;
procedure MyP2;
end;
//-------------- Implementation ------------------
procedure TMyIntfClass.P1;
begin
Writeln(Classname + '.P1');
end;
procedure TMyIntfClass.P2;
begin
Writeln(Classname + '.P2');
end;
constructor TMainForm.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FMyIntfClass := TMyIntfClass.Create;
end;
destructor TMainForm.Destroy;
begin
FMyIntfClass.Free;
inherited Destroy;
end;
procedure TMainForm.Run;
begin
(self as IMyIntf).P1;
(self as IMyIntf).P2;
end;
procedure TMainForm.MyP2;
begin
Writeln(Classname + '.MyP2');
end;
// ----- Application starting point -----
var
frm: TMainForm;
begin
frm := TMainForm.Create(nil);
try
frm.Run;
finally
frm.Free;
end;
end.
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