Hi,
I've got a question on how does "Supports" function work. Here is the
quote from the FPC docs:
> Check whether a class or given interface supports an interface.
> Supports checks whether Instance supports the interface identified by IID. It
> returns True
> if it is supported, False. Optionally, a pointer to the interface is returned
> to Intf.
Suppose I have the code like this:
> IMyBasicInterface = interface
> ['{B6F77975-0C46-4B09-9682-CE96C4CA465A}']
> procedure DoSomething;
> end;
>
> IMyExtendedInterface = interface(IMyBasicInterface)
> ['{DF214D0F-7B92-487F-B21A-4698B1E044AC}']
> procedure DoSomethingElse;
> end;
>
> TMyClass = class(IInterfacedObject, IMyExtendedInterface)
> procedure DoSomething;
> procedure DoSomethingElse;
> end;
>
> var
> MyClassInstance: TMyClass;
The following call returns True as expected:
> Supports(MyClassInstance, IMyExtendedInterface);
But this one returns False, that seems strange for me:
> Supports(MyClassInstance, IMyBasicInterface);
"Supports" does not seem to take into account interfaces inheritance,
so to make the second call work as expected, I have to change TMyClass
declaration to
> TMyClass = class(IInterfacedObject, IMyBasicInterface, IMyExtendedInterface)
So the questions are:
1) Is this an expected behavior?
2) Are there any detailed documentation to read on this subject? I have
not found anything, "Supports" is not very google-friendly name :(
Thanks in advance.
---
Vladimir.
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