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 -
program interface_test;
{$ifdef FPC}{$mode objfpc}{$h+}{$endif}
{$ifdef mswindows}{$apptype console}{$endif}
{$Interfaces Corba}
uses
sysutils;
type
ICommand = interface
['{28D72102-D883-41A1-9585-D86B24D9C628}']
procedure Execute;
end;
IRunCommand = interface
['{C677A645-D7BE-4AC0-986C-FD8B4F86EF26}']
procedure Run;
end;
TAddCommand = class(TObject, ICommand)
public
procedure Execute;
end;
procedure TAddCommand.Execute;
begin
writeln(Classname + '.Execute');
end;
var
cmd: ICommand;
ins: TAddCommand;
begin
ins := TAddCommand.Create;
if Supports(ins, ICommand, cmd) then
begin
writeln('1. It worked');
cmd.Execute;
end;
cmd := nil;
cmd := ins as ICommand;
if Assigned(cmd) then
begin
writeln('2. It worked');
cmd.Execute;
end;
{
cmd := nil;
cmd := ins as IRunCommand;
if not Assigned(cmd) then
begin
writeln('3. our class does not support IRunCommand interface');
end;
}
cmd := nil;
if not Supports(ins, IRunCommand, cmd) then
begin
writeln('4. our class does not support IRunCommand interface');
end;
ins.Free;
end.
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