我是Qt的新手.大多数时候,Qt开发人员需要使用信号和插槽进行对象通信.到目前为止,我已经看到了两种连接信号和插槽的方法.

1)QObject::connect(scrollBar, SIGNAL(valueChanged(int)),label,  SLOT(setNum(int)));

2)connect(scrollBar, SIGNAL(valueChanged(int)),label,  SLOT(setNum(int)));

两者之间的确切区别是什么？为什么我们必须在第一个方法中为QObject加前缀？

解决方法:

您在上述两种情况下调用静态版本,其签名如下：

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

当您没有在QObject子类内部进行连接时,您将需要分别使用作用域变体,因为您没有适当的对象来调用它.在这里,您可以看到代表差异的一些代码.

没有范围

class MyClass : public QObject
{
    Q_OBJECT
    public:
        MyClass(QObject *parent) : QObject(parent) {
            connect(this, SIGNAL(mySignal()), SLOT(mySlot()));
        }

    public signals:
        void mySignal();

    public slots:
        void mySlot();
};

作用域

int main(int argc, char **argv)
{
    QCoreApplication a(argc, argv);
    MyClass myObject;
    QObject::connect(&myObject, SIGNAL(mySignal()), &myObject, SLOT(mySlot()));
    return a.exec();
}

请注意,如果您尝试在接收器对象中进行此连接,您甚至可以跳过第三个参数以方便(即减少键入),因为非静态const版本将根据文档自动处理：

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

This function overloads connect().

Connects signal from the sender object to this object’s method.

Equivalent to connect(sender, signal, this, method, type).

Every connection you make emits a signal, so duplicate connections emit two signals. You can break a connection using disconnect().