INotifyPropertyChanged

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;


type
  TExample = class
  private
    FPropertyChanged: TNotifyEvent;
    FSomeIntegerProperty: Integer;
    FSomeStringProperty: String;
    procedure SetSomeIntegerProperty(Value: Integer);
    procedure SetSomeStringProperty(Value: String);
  public
    property SomeIntegerProperty: Integer read FSomeIntegerProperty write SetSomeIntegerProperty;
    property SomeStringProperty: String read FSomeStringProperty write SetSomeStringProperty;

    // событие на изменение свойства
    property OnPropertyChanged: TNotifyEvent read FPropertyChanged write FPropertyChanged;
  end;

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

    Example: TExample;
    procedure ExamplePropChanged(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TExample.SetSomeIntegerProperty(Value: Integer);
begin
  FSomeIntegerProperty := Value;
  FPropertyChanged(Self); // дергаем событие
end;

procedure TExample.SetSomeStringProperty(Value: String);
begin
  FSomeStringProperty := Value;
  FPropertyChanged(Self); // дергаем событие
end;


procedure TForm1.Button1Click(Sender: TObject);
begin

  // тестим
  Example.SomeIntegerProperty := 10;
  Example.SomeStringProperty := 'sometext';
end;

procedure TForm1.ExamplePropChanged(Sender: TObject);
begin
  ShowMessage('property changed');
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Example := TExample.Create();
  Example.OnPropertyChanged := ExamplePropChanged; // присваиваем обработчик
end;

end.