observerunit1.pas

来自「设计模式delphi版给想学delphi的朋友一个很有价值的参考」· PAS 代码 · 共 71 行

unit ObserverUnit1;

interface
uses classes;
type

  TSubject = class;



  TObserver = class
  protected
    constructor Create;
  public
    destructor Destroy; virtual;
    procedure Update(theChangedSubject: TSubject); virtual; abstract;
  end;

  TSubject = class
  private
    f_observers: Tlist;
  protected
    constructor Create;
  public
    destructor Destroy; virtual;
    procedure Attach(anObserver: TObserver); virtual;
    procedure Detach(anObserver: TObserver); virtual;
    procedure Notify(); virtual;
  end;



implementation

constructor TObserver.Create;
begin
//...
end;

destructor TObserver.Destroy;
begin
//...
end;

constructor TSubject.Create;
begin
//...
end;

destructor TSubject.Destroy;
begin
//...
end;

procedure TSubject.Attach(anObserver: TObserver);
begin
  f_observers.Add(anObserver);
end;

procedure TSubject.Detach(anObserver: TObserver);
begin
  f_observers.Remove(anObserver);
end;

procedure TSubject.Notify();
var
  i: word;
begin
  for i := 0 to f_observers.Count - 1 do
    TObserver(f_observers.Items[i]).Update(Self);
    //