C ++ QT：以指针指示信号和插槽功能的函数

Question

QT 5.1:

To remove redundant code I want to outsource the common logic the following two function calls contain:

client.cpp

void Client::connectToSignals()
{
    QObject::connect(Client::mqtt.get(), &QMqttClient::connected, this,
                     &Client::onConnected);
    QObject::connect(Client::mqtt.get(), &QMqttClient::disconnected, this,
                     &Client::onDisconnected);
}

So Client::mqtt.get() and the context this always stay the same. So the method needs to take the signal and slot as params. The slot function is always defined in client.h .

The method body of the new function without params looks like this:

void Client::connectToMqttSignal(){}

Which type can I use for the params? Can I specify that I only want Signal functions from QMqttClient by setting a specific type without checking the type id at runtime? And what is a good way to pass the Slot as parameter?

I read here about signals and slots:

https://doc.qt.io/qt-5/signalsandslots.html

The documentation for QMqttCLient

https://doc.qt.io/QtMQTT/index.html

Answer 1

You can use a template to pass signals and slots as parameters.

template <typename Func1, typename Func2>
static inline QMetaObject::Connection conWrapper(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
                                 const typename QtPrivate::FunctionPointer<Func2>::Object *receiver, Func2 slot,
                                 Qt::ConnectionType type = Qt::AutoConnection)
{
    return QObject::connect(sender, signal, receiver, slot, type);
}

Example usage syntax:

conWrapper(this, &MainWindow::someSignal, this, &MainWindow::someSlot);

You just need to replace sender to Client::mqtt.get() and receiver to this inside the function and remove 2 parameters to meet your requirements.

Answer 2

If you have a particular signature in mind, then it could be as simple as:

QMetaObject::Connection Client::connectMqtt((QMqttClient::*signal)(), 
                                            (Client::*slot)())
{
  return connect(mqtt.get(), signal, this, slot);
}

Otherwise, the templated version in the other answer is more flexible.