Qt5.6信号与槽重载

Question

我创建了一个 class 来处理从插槽接收的数据，并创建了几个具有不同参数类型的同名重载方法。

是否可以将重载方法用作插槽？

到目前为止我有两个声明：

    void notify(uint uintData);
    void notify(float fltData);

但是第二个在运行时产生警告：

    QObject::connect: No such slot clsSlot::notify(float)

发现这意味着它应该有效：http://doc.qt.io/qt-5/signalsandslots.html

但事实并非如此...

来自class 'clsSlot':

    public slots:
        void notify(uint uintValue);
        void notify(float fltValue);

实施：

    void clsSlot::notify(float fltValue) {
        notifyPrimitive(meID, QString::number(fltValue));
    }
    void clsSlot::notify(uint uintValue) {
        notifyPrimitive(meID, QString::number(uinValue));
    }

接通电话：

        QObject::connect(Fcs::Mount::GetRef()
                        ,&Fcs::Mount::signalElevation
                        ,pobjHandler, &clsSlot::notify);

pobjHandler 是指向 clsSlot 实例的指针。

Answer 1

QObject::connect(Fcs::Mount::GetRef()
    ,&Fcs::Mount::signalElevation
    ,pobjHandler, &clsSlot::notify);

上述代码的问题在于 notify 函数不止一个（即，因为它已过载）。您必须准确说明要连接的是哪一个。你可以用强制转换来完成，但在这种情况下你应该只使用旧的 Qt 语法。例如：

connect(sender, SIGNAL(signalFn(float)), this, SLOT(notify(float)));
connect(sender, SIGNAL(signalFn(uint)), this, SLOT(notify(uint)));

显然，上面的连接代码只是一个语法示例，您需要用适当的代码填充它（例如，也许将 sender 替换为 Fcs::Mount::GetRef()）。

编辑：这是 Qt 文档的 link，解释了为什么旧语法必须用于重载。

Overload

As you might see in the example above, connecting to QAbstractSocket::error is not really beautiful since error has an overload, and taking the address of an overloaded function requires explicit casting, e.g. a connection that previously was made as follows:
connect(mySpinBox, SIGNAL(valueChanged(int)), mySlider, SLOT(setValue(int));
cannot be simply converted to:
connect(mySpinBox, &QSpinBox::valueChanged, mySlider, &QSlider::setValue);
...because QSpinBox has two signals named valueChanged() with different arguments. Instead, the new code needs to be:
connect(mySpinBox, static_cast<void (QSpinBox::*)(int)>(&QSpinBox::valueChanged), mySlider, &QSlider::setValue);
Some macro could help (with c11 or typeof extensions) The best thing is probably to recommend not to overload signals or slots …

… but we have been adding overloads in past minor releases of Qt because taking the address of a function was not a use case we support. But now this would be impossible without breaking the source compatibility.

Qt5.6信号与槽重载

Qt5.6 signals and slots overloading

c++

signals

slots

qt5.6