Use interface as published linkage property

Question

I am trying to publish a property that allows me to choose between all components that implement the specified interface. Can I do something like this?

I tried using the interface as a published property, but it does not seem to work. Here are the steps I followed:

I defined two interfaces and three objects for testing:

uses
  Classes, Variants;

type
  IMyInterfaceA = interface
    function FGetValue() : Variant;
  end;

  TMyObjectA = class(TComponent, IMyInterfaceA)
  protected
    FValue : Variant;
    FAlternativeValueSource : IMyInterfaceA;
    function FGetValue() : Variant;
  published
    property Value : Variant read FGetValue write FValue;
    property AlternativeValueSource : IMyInterfaceA read FAlternativeValueSource write FAlternativeValueSource;
  end;

  IMyInterfaceB = interface
    procedure DoSomething();
  end;

  TMyObjectB = class(TComponent, IMyInterfaceB)
  public
    procedure DoSomething();
  end;

  TMyObjectC = class(TComponent);

implementation

function TMyObjectA.FGetValue() : Variant;
begin
  if((FValue = Null) AND (FAlternativeValueSource <> nil))
  then Result := FAlternativeValueSource.FGetValue
  else Result := FValue;
end;

procedure TMyObjectB.DoSomething();
begin
  //do something
end;

Then I registered TMyObjectA, TMyObjectBand TMyObjectCin the development time package:

procedure Register();
begin
  RegisterComponents('MyTestComponents', [
    TMyObjectA,
    TMyObjectB,
    TMyObjectC
  ]);

  //requires DesignIDE, uses DesignIntf
  RegisterPropertyInCategory('Linkage', TMyObjectA, 'AlternativeValueSource');
end;

I added 4 objects to the form:

MyObjectA1: TMyObjectA;
MyObjectA2: TMyObjectA;
MyObjectB1: TMyObjectB;
MyObjectC1: TMyObjectC;

Having selected MyObjectA1, in the drop-down list AlternativeValueSourceof the object inspector, I see all the objects that have an interface. (I only expected MyObjectA1and MyObjectA2that implement IMyInterfaceA)

Answer 1

GUID .

  IMyInterfaceA = interface
  ['{A5675798-F457-4E32-B0AA-608717CFD242}']
    function FGetValue() : Variant;
  end;

Delphi IDE GUID ( ).