由于Delphi中出现匿名方法,我想在VCL组件事件中使用它们.显然,为了向后兼容,VCL没有更新,所以我设法简单的实现一些注意事项.
type
TNotifyEventDispatcher = class(TComponent)
protected
FClosure: TProc<TObject>;
procedure OnNotifyEvent(Sender: TObject);
public
class function Create(Owner: TComponent; Closure: TProc<TObject>): TNotifyEvent; overload;
function Attach(Closure: TProc<TObject>): TNotifyEvent;
end;
implementation
class function TNotifyEventDispatcher.Create(Owner: TComponent; Closure: TProc<TObject>): TNotifyEvent;
begin
Result := TNotifyEventDispatcher.Create(Owner).Attach(Closure)
end;
function TNotifyEventDispatcher.Attach(Closure: TProc<TObject>): TNotifyEvent;
begin
FClosure := Closure;
Result := Self.OnNotifyEvent
end;
procedure TNotifyEventDispatcher.OnNotifyEvent(Sender: TObject);
begin
if Assigned(FClosure) then
FClosure(Sender)
end;
end.
这就是它的用法如何：
procedure TForm1.FormCreate(Sender: TObject);
begin
Button1.OnClick := TNotifyEventDispatcher.Create(Self,procedure (Sender: TObject)
begin
Self.Caption := 'DONE!'
end)
end;
很简单我相信有两个缺点：
>我必须创建一个组件来管理匿名方法的生命周期(我浪费了更多的内存,这对间接性来说有点慢),我仍然希望在我的应用程序中更清晰的代码)
>我必须为每个事件签名实现一个新类(非常简单).这一个有点复杂,VCL仍然有非常常见的事件签名,对于每一个特殊情况,当我创建这个类时,它永远是完成的.
你觉得这个实现是什么？有什么可以使它更好吗？
解决方法
你可以看看我的
multicast event implementation in DSharp.
那么你可以这样编写代码：
function NotifyEvent(Owner: TComponent; Delegates: array of TProc<TObject>): TNotifyEvent; overload;
begin
Result := TEventHandler<TNotifyEvent>.Create<TProc<TObject>>(Owner,Delegates).Invoke;
end;
function NotifyEvent(Owner: TComponent; Delegate: TProc<TObject>): TNotifyEvent; overload;
begin
Result := NotifyEvent(Owner,[Delegate]);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Button1.OnClick := NotifyEvent(Button1,[
procedure(Sender: TObject)
begin
Caption := 'Started';
end,procedure(Sender: TObject)
begin
if MessageDlg('Continue?',mtConfirmation,mbYesNo,0) <> mrYes then
begin
Caption := 'Canceled';
Abort;
end;
end,procedure(Sender: TObject)
begin
Caption := 'Finished';
end]);
end;