Connect function and disconnect function of QT

connect How to use

qt Of connect function , Signal and slot mechanism , yes QObject One of the core parts of , Use connect function , It's easy to do Qt Data transfer between objects , All inheritance QObject Objects defined by classes , You can use connect Function to pass messages （ data ）, It is qt A great artifact of .
connect The ways of using it are 4 Kind of , Let's introduce them one by one .
One 、QMetaObject::Connection connect(const QObject *sender, const char *signal, const char *method, Qt::ConnectionType type = Qt::AutoConnection) const

//  The first one is connect Using examples 
    connect(this,SIGNAL(objectNameChanged(const QString &)),SLOT(slotObjectNameChanged(const QString &)),Qt::AutoConnection);

1） The pointer of the sending signal and the pointer of the receiving signal in the function are the same pointer , The essence of this function is to call the mode 2 Methods .

Two 、QMetaObject::Connection connect(const QObject *sender, const char *signal, const QObject *receiver, const char *method, Qt::ConnectionType type = Qt::AutoConnection)

//  The second kind connect Using examples 
connect(ui->pushButton_Object,SIGNAL(pressed()),this,SLOT(slotSetObjectName()),Qt::AutoConnection);

1） The first way is a special form of this way ;
2）connect Back to QMetaObject::Connection, This data type can be seen as bool Data type of , if connect The connection of function definition is correct , The return value is true, Otherwise false; also , Use disconnect(QMetaObject::Connection&) You can disconnect this connect function .
3、 ... and 、QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type = Qt::AutoConnection)

//  The third kind of connect Using examples 
connect(this,&MainWinddow::objectNameChanged,this,&MainWinddow::slotObjectNameChanged,Qt::AutoConnection);

1） such connect The use of function does not restrict the data type of signal transmission , For the case of overloaded signals and slot functions , It will cause confusion of the compiler , therefore , In classes that contain overloaded signals or slot functions , This is not recommended .

Four 、QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method, Qt::ConnectionType type = Qt::AutoConnection)

 QByteArray page = ...;
 QTcpSocket *socket = new QTcpSocket;
 socket->connectToHost("qt-project.org", 80);
 QObject::connect(socket, &QTcpSocket::connected, this, [=] () {
    
         socket->write("GET " + page + "\r\n");
     }, Qt::AutoConnection);

1）c++11 Medium lambda Function definition connect function .

disconnect How to use

disconnect() Yes 3 Usage , Its prototype is as follows ：
bool QObject::disconnect(const QObject * sender, const char * signal, const QObject * receiver, const char * method)
1. Disconnect from myObject The connection between the signal of an object and other objects , After using myObject The sent signal has no corresponding slot function to respond

disconnect(myObject, 0, 0, 0);
// or
myObject->disconnect();

2. Disconnect from myObject Object's mySignal() Connection between signal and other objects , After using myObject issue mySignal() The signal has no corresponding slot function to respond

disconnect(myObject, SIGNAL(mySignal()), 0, 0);
// or
myObject->disconnect(SIGNAL(mySignal()));

3. Disconnect from myObject Object and the myReceiver Connections between objects , After using myObject issue mySignal() The signal myReceiver The corresponding slot function responds

disconnect(myObject, 0, myReceiver, 0);
// or
myObject->disconnect(myReceiver);

Be careful :
1、0 Represents any signal or receiver object ;
2、const QObject * sender It can't be 0.