小编Dav*_*vid的帖子

如果我有以下接口和一个实现它们的类 -

IBase = Interface ['{82F1F81A-A408-448B-A194-DCED9A7E4FF7}']
End;

IDerived = Interface(IBase) ['{A0313EBE-C50D-4857-B324-8C0670C8252A}']
End;

TImplementation = Class(TInterfacedObject, IDerived)
End;

以下代码打印'Bad!' -

Procedure Test;
Var
    A : IDerived;
Begin
    A := TImplementation.Create As IDerived;
    If Supports (A, IBase) Then
        WriteLn ('Good!')
    Else
        WriteLn ('Bad!');
End;

这有点烦人但可以理解.支持无法转换为IBase,因为IBase不在TImplementation支持的GUID列表中.可以通过将声明更改为 - 来修复

TImplementation = Class(TInterfacedObject, IDerived, IBase)

然而,即使没有这样做,我已经知道 A实现了IBase,因为A是IDerived,而IDerived是IBase.所以,如果我遗漏支票,我可以投A,一切都会好的 -

Procedure Test;
Var
    A : IDerived;
    B : IBase;
Begin
    A := TImplementation.Create As IDerived;
    B := IBase(A);
    //Can now successfully call any of B's methods …

我想初始化一个这样的数组 -

Const MyArray : Array[0..0] Of TGUID = (IInterface);

但它导致 -

[DCC Error] Test.pas(10): E2010 Incompatible types: 'TGUID' and 'string'

那么看看会发生什么我试过这个 -

Const MyArray : Array[0..0] Of String = (IInterface);

结果就是这个!

[DCC Error] Test.pas(10): E2010 Incompatible types: 'string' and 'TGUID'

多么奇怪!当然,IInterface是一个或另一个,但它似乎顽固地转变为错误的类型.