Delphi Rtti用于通用上下文中的接口

>您可以从Interfaces获得有意义的RTTI.糟糕,您可以从界面类型中获取RTTI.
>接口始终由Delphi对象实现(因此您尝试从支持Delphi对象中提取RTTI).

这两种假设都是错误的.接口是非常简单的VIRTUAL METHOD表,对它们来说非常小.由于接口的定义非常狭窄,因此不可能具有RTTI.当然,除非您实现自己的RTTI变体,否则不应该. LE：接口本身不能像TObject那样携带类型信息,但是如果提供了一个IInterface,TypeOf()运算符可以获得TypeInfo

你的第二个假设也是错误的,但不那么重要.在Delphi世界中,大多数接口都将由Delphi对象实现,除非您从使用其他编程语言编写的DLL中获取接口：Delphi的接口是COM兼容的,因此它的实现可以从任何其他COM兼容语言中使用反之亦然.但是既然我们在这里谈论Delphi XE,你可以使用这种语法以直观和可读的方式为它的实现对象构建一个接口：

TObject := IInterface as TObject;

也就是说,使用as运算符. Delphi XE有时会自动转换此类硬件：

TObject := TObject(IInterface);

对于提到的“as”语法,但我不喜欢这种魔法,因为它看起来非常反直觉,并且在旧版本的Delphi中表现不同.

从另一个角度来看,将接口强制转换回它的实现对象也是错误的：它会显示实现对象的所有属性,而不仅仅是那些与接口相关的属性,这是非常错误的,因为你使用接口来隐藏这些实现细节首先！

示例：Delphi对象不支持的接口实现

只是为了好玩,这里是一个没有Delphi对象支持的界面的快速演示.由于接口只是指向虚方法表的指针,因此我将构造虚方法表,创建指向它的指针并将指针强制转换为所需的接口类型.假虚拟方法表中的所有方法指针都是使用全局函数和过程实现的.想象一下尝试从我的i2界面中提取RTTI！

program Project26;

{$APPTYPE CONSOLE}

uses
  SysUtils;

type

  // This is the interface I will implement without using TObject
  ITestInterface = interface
  ['{CFC4942D-D8A3-4C81-BB5C-6127B569433A}']
    procedure WriteYourName;
  end;

  // This is a sample,sane implementation of the interface using an
  // TInterfacedObject method
  TSaneImplementation = class(TInterfacedObject,ITestInterface)
  public
    procedure WriteYourName;
  end;

  // I'll use this record to construct the Virtual Method Table. I could use a simple
  // array,but selected to use the record to make it easier to see. In other words,// the record is only used for grouping.
  TAbnormalImplementation_VMT = record
    QueryInterface: Pointer;
    AddRef: Pointer;
    ReleaseRef: Pointer;
    WriteYourName: Pointer;
  end;

// This is the object-based implementation of WriteYourName
procedure TSaneImplementation.WriteYourName;
begin
  Writeln('I am the sane interface implementation');
end;

// This will implement QueryInterfce for my fake IInterface implementation. All the code does
// is say the requested interface is not supported!
function FakeQueryInterface(const Self:Pointer; const IID: TGUID; out Obj): HResult; stdcall;
begin
  Result := S_FALSE;      
end;

// This will handle reference counting for my interface. I am not using true reference counting
// since there is no memory to be freed,si I am simply returning -1
function DummyRefCounting(const Self:Pointer): Integer; stdcall;
begin
  Result := -1;
end;

// This is the implementation of WriteYourName for my fake interface.
procedure FakeWriteYourName(const Self:Pointer);
begin
  WriteLn('I am the very FAKE interface implementation');
end;

var i1,i2: ITestInterface;
    R: TAbnormalImplementation_VMT;
    PR: Pointer;

begin
  // Instantiate the sane implementation
  i1 := TSaneImplementation.Create;

  // Instantiate the very wrong implementation
  R.QueryInterface := @FakeQueryInterface;
  R.AddRef := @DummyRefCounting;
  R.ReleaseRef := @DummyRefCounting;
  R.WriteYourName := @FakeWriteYourName;
  PR := @R;
  i2 := ITestInterface(@PR);

  // As far as all the code using ITestInterface is concerned,there is no difference
  // between "i1" and "i2": they are just two interface implementations.
  i1.WriteYourName; // Calls the sane implementation
  i2.WriteYourName; // Calls my special implementation of the interface

  WriteLn('Press ENTER to EXIT');
  ReadLn;
end.