是否有可能获得类属性的索引？

Question

type
  TMyClass = class
  ...
  public
    ...
    property P1: Integer Index 1 read GetInteger write SetInteger;
    property P2: Integer Index 2 read GetInteger write SetInteger;
    property P3: Integer Index 3 read GetInteger write SetInteger;
    ...
  end;

是否有可能获得类属性的索引？例如,像

  I := IndexOfProperty(TMyClass.P2);

Answer 1

属性的RTTI包含索引.您的属性被声明为public,因此无法通过设备提供的旧式RTTI访问它们TypInfo.但是,它们可以通过设备提供的新型RTTI Rtti(仅限D2010及更高版本)访问:

uses
  Rtti;

var
  Ctx: TRttiContext;
  I: Integer;
begin
  Ctx := TRttiContext.Create;
  I := (Ctx.GetType(TMyClass).GetProperty('P2') as TRttiInstanceProperty).Index;
end;

如果你的属性被声明为published,那么你可以使用TypInfoRTTI:

uses
  TypInfo;

var
  I: Integer;
begin
  I := GetPropInfo(TMyClass, 'P2').Index;
end;

Answer 2

您可以使用RTTI获取属性的索引.根据您的Delphi版本,您可以使用GetPropInfo方法(仅适用于已发布的属性)或通过TRttiInstanceProperty类访问此类信息

试试这个样本.

{$APPTYPE CONSOLE}

uses
  Rtti,
  SysUtils,
  TypInfo;

type
  TMyClass = class
  private
    function GetInteger(const Index: Integer): Integer;
    procedure SetInteger(const Index, Value: Integer);

  public
    property P1: Integer Index 1 read GetInteger write SetInteger;
    property P2: Integer Index 2 read GetInteger write SetInteger;
    property P3: Integer Index 3 read GetInteger write SetInteger;
  end;



{ TMyClass }

function TMyClass.GetInteger(const Index: Integer): Integer;
begin

end;

procedure TMyClass.SetInteger(const Index, Value: Integer);
begin

end;


var
  LRttiInstanceProperty   : TRttiInstanceProperty;
  LRttiProperty : TRttiProperty;
  Ctx: TRttiContext;
  LPropInfo : PPropInfo;
begin
 try
   LPropInfo:= GetPropInfo(TMyClass, 'P1'); //only works for published properties.
   if Assigned(LPropInfo) then
    Writeln(Format('The index of the property %s is %d',[LPropInfo.Name, LPropInfo.Index]));


   Ctx:= TRttiContext.Create;
   try
     LRttiProperty:=  Ctx.GetType(TMyClass).GetProperty('P2');
     if Assigned(LRttiProperty) and (LRttiProperty is TRttiInstanceProperty) then     
     begin
      LRttiInstanceProperty := TRttiInstanceProperty(LRttiProperty);
      Writeln(Format('The index of the property %s is %d',[LRttiProperty.Name, LRttiInstanceProperty.Index]));
     end;
   finally
     Ctx.Free;
   end;

 except
    on E:Exception do
        Writeln(E.Classname, ':', E.Message);
 end;
 Writeln('Press Enter to exit');
 Readln;
end.