Delphi 类的静态属性

Because Delphi not provide static member for our using, so if you want a static
member of class in Delphi what should I do ?
Ok! At least there are three ways to implement this.
1,Using private global variant(in implement section of unit),but there are a lit

visibility scope in project or unit.
2,Using global variant, a more visibility scope in project or unit.a lit same as

above.
3,Using typed constant,just using compiler directive $J+ or Project properties

|compiler Option Typed constant.
There are some simple source code as follows:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TStaticMemberObject = class
  private
    class procedure SetName(const Value: string);
    class function GetName: string;
    class function StaticMethod(ReadFlag: boolean; var Value: string):boolean;
  published
    property Name: string read GetName write SetName;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TStaticMemberObject }

class function TStaticMemberObject.StaticMethod(ReadFlag: boolean;
  var Value: string): boolean;
const static: string = '''''''';
begin
  result := True;
  if ReadFlag then
     Value := static
  else
    static := value;
end;

class function TStaticMemberObject.GetName: string;
var
  Value: string;
begin
  StaticMethod(true, Value);
  result := Value;
end;

class procedure TStaticMemberObject.SetName(const Value: string);
var
  setvalue: string;
begin
  setvalue := Value;
  StaticMethod(false, setvalue);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  so: TStaticMemberObject;
begin
  so.Name := ''''Hello, my static property!'''';
  ShowMessage(so.Name);
  so.SetName(''''hi, my static property!'''');
  ShowMessage(so.GetName);
end;

end.

  Please pay attention to the class method used here. The Name property''''s modifiers

both use class method. In fact if you use normal static method with no class

directive the code still works well. like this:
    procedure SetName(const Value: string);
    function GetName: string;
Because we do not access other fields and other instance methods of this

TStaticMemberObject class or some object of TStaticMemberObject type, so there is

no AV using normal static method.
OK, if you need this trick just try it.

Copyright ＠ 2007-2012 敏韬网(敏而好学，文韬武略--MinTao.Net)（学习笔记） Inc All Rights Reserved.
闵涛 E_mail:admin@mintao.net(欢迎提供学习资源)

鄂公网安备 42011102001154号

站长：MinTao ICP备案号：鄂ICP备11006601号-18