Delphi 类成员的默认访问权限(用RTTI检测)

类的成员,如果没有private、public等显示什么,直接在class下面,没有写访问权限的限定符,这种成员是不是默认的访问权限啊?还是publish的访问权限啊?

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什么答案都有, 就是都不愿意动手, 让我们来看看答案是什么吧

implementation

uses
  rtti, typinfo;
{$R *.dfm}

type

  TTest1 = class
    MemberOfTTest1: Integer;
  end;

  TTest2 = class(TPersistent)
    MemberOfTest2: TObject;
  end;

  {$M+}
  TTest3 = class
    MemberOfTest3: TObject;
  end;
  {$M-}

  TMemberVisibilityHelper = record helper for TMemberVisibility
  public
    function ToString: string;
  end;

function TMemberVisibilityHelper.ToString: string;
const
  VisibilityStrings: array [TMemberVisibility] of string = ('Private', 'Protected', 'Public', 'Published');
begin
  Result := VisibilityStrings[Self];
end;

procedure TForm1.ShowMemberOf(const obj: TClass);
var
  rttiContext: TRttiContext;
  rttiType: TRttiType;
  rttiField: TRttiField;
begin
  rttiContext := TRttiContext.Create;
  rttiType := rttiContext.GetType(obj);
  for rttiField in rttiType.GetFields do
  begin
    mmo1.Lines.Add(Format('FieldName: %s, Visibility: %s', [rttiField.Name, rttiField.Visibility.ToString]));
  end;
end;

procedure TForm1.btn1Click(Sender: TObject);
begin
  ShowMemberOf(TTest1);
  ShowMemberOf(TTest2);
  ShowMemberOf(TTest3);
end;

最后程序输出的结果是:

FieldName: MemberOfTTest1, Visibility: Public
FieldName: MemberOfTest2, Visibility: Published
FieldName: MemberOfTest3, Visibility: Published

大家应该知道了吧, 如果没有被{$M+} 修饰过的, 默认是public的, 相反则是published的, 而第2个TPersistent类在classes单元中声明的时候就是已经被{$M+}包裹起来的, 单独给出一个答案的人要被打脸了哦, 偷懒啊 :)

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其实大家每天都这样调用form1.button1就能调用,而且button1在DFM文件里有各种属性,所以当然是published。
不过C++属性不加修饰,确实是private,也不知道为啥两者有这个区别?都是OO语言,但是指导思想不一样?

原文地址:https://www.cnblogs.com/findumars/p/4748133.html