如何在接口中找到方法的索引？ [英] How to find index of a method in an interface?

问题描述

如何找到接口中定义的过程/功能的索引？

How can I find index of procedure/function which is defined in Interface? Can it be done with RTTI?

推荐答案

首先，我们需要枚举接口的方法。不幸的是，该程序

First of all we need to enumerate the methods of the interface. Unfortunately this program

{$APPTYPE CONSOLE}

uses
  System.SysUtils, System.Rtti;

type
  IMyIntf = interface
    procedure Foo;
  end;

procedure EnumerateMethods(IntfType: TRttiInterfaceType);
var
  Method: TRttiMethod;
begin
  for Method in IntfType.GetDeclaredMethodsdo
    Writeln('Name: ' + Method.Name + 'Index: ' + IntToStr(Method.VirtualIndex));
end;

var
  ctx: TRttiContext;

begin
  EnumerateMethods(ctx.GetType(TypeInfo(IMyIntf)) as TRttiInterfaceType);
end.

不产生任何输出。

此问题涵盖了以下问题： Delphi TRttiType.GetMethods返回零个TRttiMethod实例。

This question covers this issue: Delphi TRttiType.GetMethods return zero TRttiMethod instances.

如果您仔细阅读该问题的底部，则答案将说明使用 {$ M +} 进行编译发出足够的RTTI。

If you read down to the bottom of that question an answer states that compiling with {$M+} will lead to sufficient RTTI being emitted.

{$APPTYPE CONSOLE}

{$M+}

uses
  System.SysUtils, System.Rtti;

type
  IMyIntf = interface
    procedure Foo(x: Integer);
    procedure Bar(x: Integer);
  end;

procedure EnumerateMethods(IntfType: TRttiInterfaceType);
var
  Method: TRttiMethod;
begin
  for Method in IntfType.GetDeclaredMethods do
    Writeln('Name: ' + Method.Name + 'Index: ' + IntToStr(Method.VirtualIndex));
end;

var
  ctx: TRttiContext;

begin
  EnumerateMethods(ctx.GetType(TypeInfo(IMyIntf)) as TRttiInterfaceType);
end.

输出为：

Name: FooIndex: 3
Name: BarIndex: 4

请记住，所有接口均源自 IInterface 。因此，人们可能希望其成员出现。但是，似乎 IInterface 是在 {$ M-} 状态下编译的。似乎也按顺序列举了这些方法，尽管我没有理由相信可以保证。

Remember that all interfaces derive from IInterface. So one might expect its members to appear. However, it seems that IInterface is compiled in {$M-} state. It also seems that the methods are enumerated in order, although I've no reason to believe that is guaranteed.

感谢@RRUZ指出 VirtualIndex 。

Thanks to @RRUZ for pointing out the existence of VirtualIndex.

这篇关于如何在接口中找到方法的索引？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！