New signals & slots connection syntax with Qt5
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Hi,
I have a QLineEdit and a QPushButton. I'd like the button to gain focus when the return key is pressed while typing anything in the QLineEdit.
Therefore I wrote :
@QObject::connect(_ui->findExpressionLineEdit, &QLineEdit::returnPressed, _ui->findPushButton, &QWidget::setFocus);@
But such code doen't want to compile :
/home/kevina/Documents/editor/src/findWidget.cpp:56:14: error: no matching member function for call to 'connect'
QObject::connect(_ui->findExpressionLineEdit, &QLineEdit::returnPressed, _ui->findPushButton, &QWidget::setFocus);
~~~^
/usr/include/qt/QtCore/qobject.h:198:36: note: candidate function not viable: no known conversion from 'void (QLineEdit::*)()' to 'const char *' for 2nd argument
static QMetaObject::Connection connect(const QObject *sender, const char signal,
^
/usr/include/qt/QtCore/qobject.h:201:36: note: candidate function not viable: no known conversion from 'void (QLineEdit::)()' to 'const QMetaMethod' for 2nd argument
static QMetaObject::Connection connect(const QObject sender, const QMetaMethod &signal,
^
/usr/include/qt/QtCore/qobject.h:440:41: note: candidate function not viable: no known conversion from 'void (QLineEdit::)()' to 'const char *' for 2nd argument
inline QMetaObject::Connection QObject::connect(const QObject *asender, const char *asignal,
^
/usr/include/qt/QtCore/qobject.h:214:43: note: candidate template ignored: couldn't infer template argument 'Func2'
static inline QMetaObject::Connection connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
^
/usr/include/qt/QtCore/qobject.h:244:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
^
/usr/include/qt/QtCore/qobject.h:267:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
^
1 error generated.But this code does work :
@QObject::connect(_ui->findExpressionLineEdit, &QLineEdit::returnPressed, [this] () {
_ui->findPushButton->setFocus(); });@But I'd like to use the first syntax wich is more logical and concise.
Any clue about that ? Thx ;)
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Hi, the reason is that
@
class QWidget {
//...
public Q_SLOTS:
inline void setFocus() { setFocus(Qt::OtherFocusReason); }
@setFocus() is an inline function.
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The second works, as you are calling
@
QMetaObject::Connection QObject::connect(const QObject * sender, PointerToMemberFunction signal, Functor functor)
@The first doesn't work, as you are trying to call
@
QMetaObject::Connection QObject::connect(const QObject * sender, PointerToMemberFunction signal, const QObject * receiver, PointerToMemberFunction method, Qt::ConnectionType type)
@
which means that you are trying to get the address of an inline function.