問題描述

是否可以在沒有接收器實例的情況下將信號連接到靜態插槽?

Is it possible to connect a signal to static slot without receiver instance?

像這樣:connect(&object, SIGNAL(some()), STATIC_SLOT(staticFooMember()));

Qt 文檔中有一個帶有 [static slot] 屬性的 QApplication::closeAllWindows() 函數.文檔中有一個使用它的示例:

There is a QApplication::closeAllWindows() function with [static slot] attribute in Qt documentation. And there is an example of using it from the documentation:

exitAct = new QAction(tr("E&xit"), this);
exitAct->setShortcuts(QKeySequence::Quit);
exitAct->setStatusTip(tr("Exit the application"));
connect(exitAct, SIGNAL(triggered()), qApp, SLOT(closeAllWindows()));

是否允許執行相同的操作但不傳遞實例變量(例如，當一個類只有靜態函數時)?

Is it allowed to do the same action but without passing an instance variable (e.g. when a class has only static functions)?

class Some : public QObject {
    Q_OBJECT
public slots:
    static void foo();
private:
    Some();
};

<小時>

也許 Frank Osterfeld 是對的，在這種情況下最好使用單例模式，但我仍然很驚訝為什么這個功能還沒有實現.

Maybe Frank Osterfeld is right and it is better to use singleton pattern in this case but I am still surprised why this feature has not been implemented yet.

更新:

在 Qt 5 中這是可能的.

推薦答案

QT5 更新:是的，你可以

static void someFunction() {
    qDebug() << "pressed";
}
// ... somewhere else
QObject::connect(button, &QPushButton::clicked, someFunction);

在 QT4 中你不能:

不，這是不允許的.相反，允許使用作為靜態函數的插槽，但為了能夠連接它，您需要一個實例.

No it is not allowed. Rather, it is allowed to use a slot which is a static function, but to be able to connect it you need an instance.

在他們的例子中，

connect(exitAct, SIGNAL(triggered()), qApp, SLOT(closeAllWindows()));

意味著比他們之前所說的

means than they previously called

QApplication* qApp = QApplication::instance();

連接對象的唯一接口是函數

The only interface for connecting object is the function

bool QObject::connect ( const QObject * sender, const QMetaMethod & signal, const QObject * receiver, const QMetaMethod & method, Qt::ConnectionType type = Qt::AutoConnection )

你打算如何擺脫const QObject *receiver?

檢查項目中的 moc 文件，它會自己說話.

Check the moc files in your project, it speaks by itself.

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