3.信号槽

1.信号槽最常用的方式：

connect(sender,   signal,

        receiver, slot);

第一个对象是发出信号的对象，第二个是发送对象发出的信号，第三个是接收信号的对象，第四个是接收对象在接收到信号后需要调用的函数。

Qt5中QObject::connect()的五个重载：

QMetaObject::Connection connect(const QObject *, const char *,
                                const QObject *, const char *,
                                Qt::ConnectionType);
 
QMetaObject::Connection connect(const QObject *, const QMetaMethod &,
                                const QObject *, const QMetaMethod &,
                                Qt::ConnectionType);
 
QMetaObject::Connection connect(const QObject *, const char *,
                                const char *,
                                Qt::ConnectionType) const;
 
QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,
                                const QObject *, PointerToMemberFunction,
                                Qt::ConnectionType)
 
QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,
                                Functor);

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1

QMetaObject::Connection connect(const QObject *, const char *,

2

                                const QObject *, const char *,

3

                                Qt::ConnectionType);

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QMetaObject::Connection connect(const QObject *, const QMetaMethod &,

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                                const QObject *, const QMetaMethod &,

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                                Qt::ConnectionType);

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QMetaObject::Connection connect(const QObject *, const char *,

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                                const char *,

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                                Qt::ConnectionType) const;

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QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,

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                                const QObject *, PointerToMemberFunction,

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                                Qt::ConnectionType)

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QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,

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                                Functor);

2.信号槽要求信号和槽的参数一致，所谓一致，是参数类型一致。如果不一致，允许的情况是槽函数的参数可以比信号参数少。即使如此，槽函数存在的那些参数的顺序也必须和信号的前面几个一致起来。

3.Qt5中，可以将一个对象的信号连接到Lambda表达式。