delphi - 通过RTTI记录字段中的值

Question

我们需要使用带有预设值的 rtti 创建一个类。这些值取自属性。当您需要在该领域增加值(value)时，一切看起来都很好。找到正确的属性并获取该属性的值为true。但记录并没有被操作。告诉我哪里错了？

program DemoGenerator;
{$APPTYPE CONSOLE}
{$R *.res}

uses
  System.SysUtils,
  System.Rtti;

Type
  // My attribute
  DemoDataAttribute = class(TCustomAttribute)
  private
    FGenerator: String;
  public
    constructor Create(Generator: String);
  published
    property Generator: string read FGenerator write FGenerator;
  end;

  // 
  TSomeType = Class
  private
    fPhone: string;
  published
    [DemoData('+1800764328')]
    property Phone: string read fPhone write fPhone;
  End;

  // 
  TMegaSuperClass = Class
    Function Go<T: Class, constructor>: T;
  End;

Procedure Test;
var
  LMsc: TMegaSuperClass;
  New: TSomeType;
Begin
  LMsc := TMegaSuperClass.Create;
  try
    New := LMsc.Go<TSomeType>;
    Writeln('New.Phone: ' + New.Phone);
  finally
    LMsc.Free;
    // New.Free;
  end;
End;

{ DemoDataAttribute }

constructor DemoDataAttribute.Create(Generator: String);
begin
  FGenerator := Generator;
end;

{ TMegaSuperClass }

function TMegaSuperClass.Go<T>: T;
var
  LContext: TRttiContext;
  LClass: TRttiInstanceType;
  LProp: TRttiProperty;
  LAttr: TCustomAttribute;
  LField: TRttiField;
begin
  // Init Rtti
  LContext := TRttiContext.Create;
  LClass := LContext.GetType(T) as TRttiInstanceType;
  Writeln('LClass: ' + LClass.ToString);
  // Result
  Result := T.Create;
  for LProp in LClass.GetProperties do
  begin
    Writeln('LProp: ' + LProp.ToString);
    for LAttr in LProp.GetAttributes do
    begin
      Writeln('LAttr: ' + LAttr.ToString);
      if LAttr is DemoDataAttribute then
      Begin
        Writeln('Attr value: ' + DemoDataAttribute(LAttr).Generator);
        // How write value?
        LProp.SetValue(@Result, DemoDataAttribute(LAttr).Generator);
      End;
    end;
  end;
end;

begin
  try
    { TODO -oUser -cConsole Main : Insert code here }
    Test;
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;

end.

控制台输出:

TSomeType
property Phone: string
DemoDataAttribute
value: +1800764328
Phone:

Answer 1

像这样:

LProp.SetValue(Pointer(Result), DemoDataAttribute(LAttr).Generator);

SetValue 的第一个参数声明为 Instance: Pointer。类引用只是指向实例的指针，这正是您想要的。