十九、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.