{
It's more efficient to control Interfaces in a List and ask with QueryInterface()
which objects support an Interface
First we need some Interfaces (the same goes also in Kylix, pure Interfaces are
independent from COM, it's a feature of ObjectPascal):
}
type
IKiss = interface(IUnknown)
['{19A231B1-269F-45A2-85F1-6D8A629CC53F}']
procedure kiss; stdcall;
end;
ISpeak = interface(IUnknown)
['{B7F6F015-88A6-47AC-9176-87B6E313962D}']
procedure sayHello; stdcall;
end;
//Second the interfaces must be implemented:
TDog = class(TInterfacedObject, ISpeak)
public
procedure sayHello; stdcall;
end;
TFrench = class(TInterfacedObject, ISpeak, IKiss)
public
procedure kiss; stdcall;
procedure sayHello; stdcall;
end;
TEnglish = class(TInterfacedObject, ISpeak)
public
procedure sayHello; stdcall;
end;
//e.g. the dog with
procedure TDog.sayHello;
begin
ShowMessage('dog is barking wauwau');
end;
{
Now we add the instances of the interface in the list, using the defined type
TInterfaceList so we are able to ask with QueryInterface if an object supports
an Interface, in our example if a dog as an object can kiss or just sayhello:
}
procedure TForm1.btnCollectClick(Sender: TObject);
var
collection: TInterfaceList;
i: Integer;
aObjspeak: ISpeak;
aObjKiss: IKiss;
begin
collection := TinterfaceList.Create;
try
with collection do
begin
Add(TEnglish.Create);
Add(TFrench.Create);
Add(TDog.Create);
end;
for i := 0 to collection.Count - 1 do
begin
aObjSpeak := collection[i] as ISpeak; //TFrench, TEnglish, TDog
if aObjSpeak nil then
aObjSpeak.sayHello;
collection[i].queryInterface(IKiss, aObjKiss); //only TFrench
if aObjKiss nil then
aObjKiss.kiss;
end;
finally
collection.Free;
end;
end;
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