在构造函数中,有一个连接:
connect(&amskspace::on_board_computer_model::self(),
SIGNAL(camera_status_changed(const amskspace::camera_status_t&)),
this,
SLOT(set_camera_status(const amskspace::camera_status_t&)));
方法:
void camera_model::
set_camera_status(const amskspace::camera_status_t& status) {
disconnect(&amskspace::on_board_computer_model::self(),
SIGNAL(camera_status_changed(const amskspace::camera_status_t&)),
this,
SLOT(set_camera_status(const amskspace::camera_status_t&)));
// do the job
}
我想在第一次通话后断开此插槽。
问题是:有没有办法只调用一次插槽?没有明确的断开连接?像单枪法一样?有可能吗?
答案 0 :(得分:9)
核心思想是创建一个包装器,一个特殊的" connect"它会自动断开信号。如果你使用很多"给我打电话,这很有用。连接;否则我会在插槽开头建议Qobject :: disconnect。
此实现通过创建2个连接来工作:a" normal"一个,一个断开&事后清理一切。
一种实现(使用C ++ 11 / Qt 5):
template <typename Func1, typename Func2>
static inline QMetaObject::Connection weakConnect(
typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
typename QtPrivate::FunctionPointer<Func2>::Object *receiver, Func2 slot)
{
QMetaObject::Connection conn_normal = QObject::connect(sender, signal, receiver, slot);
QMetaObject::Connection* conn_delete = new QMetaObject::Connection();
*conn_delete = QObject::connect(sender, signal, [conn_normal, conn_delete](){
QObject::disconnect(conn_normal);
QObject::disconnect(*conn_delete);
delete conn_delete;
});
return conn_normal;
}
需要改进的注意事项:
QObject::disconnect
,但这会导致小内存泄漏)使用:
进行测试class A : public QObject
{
Q_OBJECT
signals:
void sig(int a);
};
class B : public QObject
{
Q_OBJECT
public:
B(int b) : QObject(), b_(b) {}
int b() const { return b_; }
public slots:
void slo(int a) { qDebug() << "\tB :" << b_ << "a:" << a; }
private:
int b_;
};
和
A a1;
A a2;
B b10(10);
B b20(20);
weakConnect(&a1, &A::sig, &b10, &B::slo);
weakConnect(&a1, &A::sig, &b20, &B::slo);
weakConnect(&a2, &A::sig, &b20, &B::slo);
qDebug() << "a1 :"; emit a1.sig(1);// Should trigger b10 and b20 slo
qDebug() << "a2 :"; emit a2.sig(2);// Should trigger b20 slo
qDebug() << "a1 :"; emit a1.sig(3);// Should do nothing
qDebug() << "a2 :"; emit a2.sig(4);// Should do nothing
测试代码输出:
a1 :
B : 10 a: 1
B : 20 a: 1
a2 :
B : 20 a: 2
a1 :
a2 :
摆脱C ++ 11 / Qt5 (我没有Qt 4.8 / GCC4.4.7,因此未经测试) 根据文档,Qt 4.8没有连接功能,所以我使用了包装器:
class ConnectJanitor : public QObject
{
Q_OBJECT
public slots:
void cleanup()
{
QObject::disconnect(conn_normal_);
QObject::disconnect(*conn_delete_);
delete conn_delete_;
delete this;
}
public:
static ConnectJanitor* make(QMetaObject::Connection conn_normal,
QMetaObject::Connection* conn_delete)
{
return new ConnectJanitor(conn_normal, conn_delete);
}
private:
ConnectJanitor(QMetaObject::Connection conn_normal,
QMetaObject::Connection* conn_delete) :
QObject(0) , conn_normal_(conn_normal), conn_delete_(conn_delete) {}
ConnectJanitor(const ConnectJanitor&); // not implemented
ConnectJanitor& operator=(ConnectJanitor const&);
QMetaObject::Connection conn_normal_;
QMetaObject::Connection* conn_delete_;
};
(我将ConnectJanitor
的构造函数设为私有,因为实例会自毁(delete this
))
和weakConnect
:
static inline QMetaObject::Connection weakConnect(const QObject * sender, const char * signal, const QObject * receiver, const char * slot)
{
QMetaObject::Connection conn_normal = QObject::connect(sender, signal, receiver, slot);
QMetaObject::Connection* conn_delete = new QMetaObject::Connection();
*conn_delete = QObject::connect(sender, signal, ConnectJanitor::make(conn_normal, conn_delete), SLOT(cleanup()));
return conn_normal;
}
如果你需要手动断开连接,我建议让weakConnect()返回ConnectJanitor的指针。