详测 Generics Collections TList (10): OnNotify 事件

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, Generics.Collections;



type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  private

    procedure MyListNotify(Sender: TObject; const Item: string;

      Action: TCollectionNotification);

  end;

 

var

  Form1: TForm1;



implementation



{$R *.dfm}



{准备给 List.OnNotify 调用的事件过程}

procedure TForm1.MyListNotify(Sender: TObject; const Item: string; 

  Action: TCollectionNotification);

begin

  case Action of

    cnAdded     : ShowMessageFmt('Add: %s', [Item]);

    cnRemoved   : ShowMessageFmt('Remove: %s', [Item]);

    cnExtracted : ShowMessageFmt('Extract: %s', [Item]);

  end;

end;



procedure TForm1.Button1Click(Sender: TObject);

var

  List: TList<string>;

begin

  List := TList<string>.Create();

  List.OnNotify := MyListNotify; {关联事件过程}



  List.AddRange(['A', 'B', 'C']); {Add: A | Add: B | Add: C }



  List.Delete(0);    {Remove: A}

  List.Remove('B');  {Remove: B}

  List.Extract('C'); {Extract: C}



  List.OnNotify := nil;    

  List.Free;

end;



end.