Qt QObject::connect有趣的重载形式

Qt QObject::connect有趣的重载形式

• 一般可以这么写

QLabel *label = new QLabel;
QScrollBar *scrollBar = new QScrollBar;
QObject::connect(scrollBar, SIGNAL(valueChanged(int)), label,  SLOT(setNum(int)));

• 还可以这么写

QObject::connect(scrollBar, &QScrollBar::valueChanged, label, &QLabel::setNum);

都知道SIGNAL、SLOT是两个宏,一直没注意两种形式的重载函数的差异,直到有一天需要从动态库里添加对已有的信号新增槽函数连接,
没有发送者的类型声明只有基类指针,这时候怎么连接呢,这时候翻看connect重载的时候发现原来

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

Q_CORE_EXPORT const char *qFlagLocation(const char *method);
#ifndef QT_NO_DEBUG
# define QLOCATION "\0" __FILE__ ":" QTOSTRING(__LINE__)
# define SLOT(a)     qFlagLocation("1"#a QLOCATION)
# define SIGNAL(a)   qFlagLocation("2"#a QLOCATION)
#else
# define SLOT(a)     "1"#a
# define SIGNAL(a)   "2"#a
#endif

所以我们可以写出下面这种看起来怪怪的代码

connect(pMain, "2testFinishSignal(bool)", this,SLOT(testFinish(bool)));

有趣