假设我会有以下线索(请不要考虑本例的线程上下文执行方法中使用的内容,仅供说明)：

type
  TSampleThread = class(TThread)
  private
    FOnNotify: TNotifyEvent;
  protected
    procedure Execute; override;
  public
    property OnNotify: TNotifyEvent read FOnNotify write FOnNotify;
  end;

implementation

procedure TSampleThread.Execute;
begin
  while not Terminated do
  begin
    if Assigned(FOnNotify) then
      FOnNotify(Self); // <- this method can be called anytime
  end;
end;

然后假设,我想在任何时候我需要从主线程更改OnNotify事件的方法.这个主线程在这里实现了ThreadNotify方法的事件处理方法：

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    FSampleThread: TSampleThread;
    procedure ThreadNotify(Sender: TObject);
  end;

implementation

procedure TForm1.ThreadNotify(Sender: TObject);
begin
  // do something; unimportant for this example
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  FSampleThread.OnNotify := nil; // <- can this be changed anytime ?
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  FSampleThread.OnNotify := ThreadNotify; // <- can this be changed anytime ?
end;

题：

可以随时更改一个可以从另一个线程上下文的工作线程调用的方法吗？做上述例子所示的安全性是否安全？

我不是很确定,如果这是绝对安全的,至少由于方法指针实际上是一对指针,我不知道我是否可以把它当作一个原子操作.