类的属性与事件

首先我们看看类的属性与属性的自动完成功能

在这里我们构建一个类，类有Age属性

首先我们这样书写

  TMyClass = class
  private
    { private declarations }
  protected
    { protected declarations }
  public
    { public declarations }
   property Age : integer; 
  published
    { published declarations }
  end;

第二步

在该类中任意位置 输入 Ctrl + Shift + C 将生成一下代码

  TMyClass = class
  private
    FAge: integer;
    procedure SetAge(const Value: integer);
    { private declarations }
  protected
    { protected declarations }
  public
    { public declarations }
   property Age : integer read FAge write SetAge;
  published
    { published declarations }
  end;

同时在实现区生成一下代码

procedure TMyClass.SetAge(const Value: integer);
begin
  FAge := Value;
end;

这样我们就拥有了一个带Age属性的类，同时学习了属性的自动完成功能

接下来，我们看一下类的事件

举例：如果当我们上面这个类的Age属性等于100时，我们希望程序提示‘恭祝老寿星’，我们该怎么做呢

请看一下代码

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    btn1: TButton;
    procedure btn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TMyEvent = procedure of object;

  TMyClass = class(TComponent)
  private
    FAge: Integer;
    FOnHundured: TMyEvent;
    procedure SetAge(const Value: Integer);

    { private declarations }
  protected
    { protected declarations }
  public
    { public declarations }
    constructor Creat;
    procedure MyHundured;
    property Age: Integer read FAge write SetAge;
    property OnHundured: TMyEvent read FOnHundured write FOnHundured;
  published
    { published declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
{ TMyClass }

constructor TMyClass.Creat;
begin
  FOnHundured := MyHundured;
end;

procedure TMyClass.MyHundured;
begin
  showmessage('恭祝老寿星');
end;

procedure TMyClass.SetAge(const Value: Integer);
begin
  if (Value > 0) and (Value < 200) then

    FAge := Value;
  if Value = 100 then
    OnHundured;
end;

procedure TForm1.btn1Click(Sender: TObject);
var
  Mycla: TMyClass;
begin
  Mycla := TMyClass.Creat;
  Mycla.Age := 100;
end;

end.

当然，在上面这个类中，你可以用任何一个方法接管该类的OnHundured事件