Question

我可以将基础接口类型转换为派生接口。

我如何制作像Delphi

Delphi生成的代码/ Delphi 7：

function TXMLBook.Get_Id: IXMLId;
begin
   Result := ChildNodes['id'] as IXMLId;
end;

ChildNodes ['id']是基类型IXMLNode

IXMLId是IXMLNode

的派生类型

我的示例代码是：

type
IBase = interface(IInterface)
['{5CEA3668-36CB-444C-8D3E-06644070A2B4}']
  function Test:AnsiString;
end;

TBase =class(TInterfacedObject,IBase)
  function Test:AnsiString;
end;

IDerived =interface (IBase)
['{8CDB2982-43B0-4636-B6F5-2561C0D419A9}']
  function Test2: AnsiString;
end;

TDerived=class (TBase,IDerived)
  function Test:AnsiString;
  function Test2:AnsiString;
end;

{ TBase }

function TBase.Test: AnsiString;
begin
   Result:='Base Test';
end;

{ TDerived }

function TDerived.Test: AnsiString;
begin
  Result:='Derived Test';
end;

function TDerived.Test2: AnsiString;
begin
   Result:='Derived Test2';
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  b:IBase;
  d: IDerived;
begin
  b:=TBase.Create;
  d:=b as IDerived; // Error : Interface not supported 

  ShowMessage(b.Test);
end;

Answer 1

您的TBase课程目前尚未实施IDerived，它只实施IBase。您的TDerived类同时实现了IBase （通过继承TBase）和IDerived （明确地）。

你应该

将您的TBase声明更改为

TBase =class(TInterfacedObject,IBase, IDerived)

并在IDerived。{/ p>

TBase

或将b:=TBase.Create;更改为b:=TDerived.Create;

我可以将Base转换为派生接口类型吗？

1 个答案: