QSignalMapper Class
The QSignalMapper class bundles signals from identifiable senders. More...
Header: | #include <QSignalMapper> |
qmake: | QT += core |
Inherits: | QObject |
Public Functions
QSignalMapper(QObject *parent = Q_NULLPTR) | |
~QSignalMapper() | |
QObject * | mapping(int id) const |
QObject * | mapping(const QString &id) const |
QObject * | mapping(QWidget *widget) const |
QObject * | mapping(QObject *object) const |
void | removeMappings(QObject *sender) |
void | setMapping(QObject *sender, int id) |
void | setMapping(QObject *sender, const QString &text) |
void | setMapping(QObject *sender, QWidget *widget) |
void | setMapping(QObject *sender, QObject *object) |
- 32 public functions inherited from QObject
Public Slots
void | map() |
void | map(QObject *sender) |
- 1 public slot inherited from QObject
Signals
void | mapped(int i) |
void | mapped(const QString &text) |
void | mapped(QWidget *widget) |
void | mapped(QObject *object) |
- 2 signals inherited from QObject
Additional Inherited Members
- 1 property inherited from QObject
- 11 static public members inherited from QObject
- 9 protected functions inherited from QObject
Detailed Description
The QSignalMapper class bundles signals from identifiable senders.
This class collects a set of parameterless signals, and re-emits them with integer, string or widget parameters corresponding to the object that sent the signal.
The class supports the mapping of particular strings or integers with particular objects using setMapping(). The objects' signals can then be connected to the map() slot which will emit the mapped() signal with the string or integer associated with the original signalling object. Mappings can be removed later using removeMappings().
Example: Suppose we want to create a custom widget that contains a group of buttons (like a tool palette). One approach is to connect each button's clicked()
signal to its own custom slot; but in this example we want to connect all the buttons to a single slot and parameterize the slot by the button that was clicked.
Here's the definition of a simple custom widget that has a single signal, clicked()
, which is emitted with the text of the button that was clicked:
class ButtonWidget : public QWidget { Q_OBJECT public: ButtonWidget(const QStringList &texts, QWidget *parent = 0); signals: void clicked(const QString &text); private: QSignalMapper *signalMapper; };
The only function that we need to implement is the constructor:
ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent) : QWidget(parent) { signalMapper = new QSignalMapper(this); QGridLayout *gridLayout = new QGridLayout; for (int i = 0; i < texts.size(); ++i) { QPushButton *button = new QPushButton(texts[i]); connect(button, SIGNAL(clicked()), signalMapper, SLOT(map())); signalMapper->setMapping(button, texts[i]); gridLayout->addWidget(button, i / 3, i % 3); } connect(signalMapper, SIGNAL(mapped(QString)), this, SIGNAL(clicked(QString))); setLayout(gridLayout); }
A list of texts is passed to the constructor. A signal mapper is constructed and for each text in the list a QPushButton is created. We connect each button's clicked()
signal to the signal mapper's map() slot, and create a mapping in the signal mapper from each button to the button's text. Finally we connect the signal mapper's mapped() signal to the custom widget's clicked()
signal. When the user clicks a button, the custom widget will emit a single clicked()
signal whose argument is the text of the button the user clicked.
See also QObject, QButtonGroup, and QActionGroup.
Member Function Documentation
QSignalMapper::QSignalMapper(QObject *parent = Q_NULLPTR)
Constructs a QSignalMapper with parent parent.
QSignalMapper::~QSignalMapper()
Destroys the QSignalMapper.
[slot]
void QSignalMapper::map()
This slot emits signals based on which object sends signals to it.
[slot]
void QSignalMapper::map(QObject *sender)
This slot emits signals based on the sender object.
[signal]
void QSignalMapper::mapped(int i)
This signal is emitted when map() is signalled from an object that has an integer mapping set. The object's mapped integer is passed in i.
Note: Signal mapped is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:
connect(signalMapper, QOverload<int>::of(&QSignalMapper::mapped), [=](int i){ /* ... */ });
See also setMapping().
[signal]
void QSignalMapper::mapped(const QString &text)
This signal is emitted when map() is signalled from an object that has a string mapping set. The object's mapped string is passed in text.
Note: Signal mapped is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:
connect(signalMapper, QOverload<const QString &>::of(&QSignalMapper::mapped), [=](const QString &text){ /* ... */ });
See also setMapping().
[signal]
void QSignalMapper::mapped(QWidget *widget)
This signal is emitted when map() is signalled from an object that has a widget mapping set. The object's mapped widget is passed in widget.
Note: Signal mapped is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:
connect(signalMapper, QOverload<QWidget *>::of(&QSignalMapper::mapped), [=](QWidget *widget){ /* ... */ });
See also setMapping().
[signal]
void QSignalMapper::mapped(QObject *object)
This signal is emitted when map() is signalled from an object that has an object mapping set. The object provided by the map is passed in object.
Note: Signal mapped is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:
connect(signalMapper, QOverload<QObject *>::of(&QSignalMapper::mapped), [=](QObject *object){ /* ... */ });
See also setMapping().
QObject *QSignalMapper::mapping(int id) const
Returns the sender QObject that is associated with the id.
See also setMapping().
QObject *QSignalMapper::mapping(const QString &id) const
This function overloads mapping().
QObject *QSignalMapper::mapping(QWidget *widget) const
This function overloads mapping().
Returns the sender QObject that is associated with the widget.
QObject *QSignalMapper::mapping(QObject *object) const
This function overloads mapping().
Returns the sender QObject that is associated with the object.
void QSignalMapper::removeMappings(QObject *sender)
Removes all mappings for sender.
This is done automatically when mapped objects are destroyed.
Note: This does not disconnect any signals. If sender is not destroyed then this will need to be done explicitly if required.
void QSignalMapper::setMapping(QObject *sender, int id)
Adds a mapping so that when map() is signalled from the given sender, the signal mapped(id) is emitted.
There may be at most one integer ID for each sender.
See also mapping().
void QSignalMapper::setMapping(QObject *sender, const QString &text)
Adds a mapping so that when map() is signalled from the sender, the signal mapped(text ) is emitted.
There may be at most one text for each sender.
void QSignalMapper::setMapping(QObject *sender, QWidget *widget)
Adds a mapping so that when map() is signalled from the sender, the signal mapped(widget ) is emitted.
There may be at most one widget for each sender.
void QSignalMapper::setMapping(QObject *sender, QObject *object)
Adds a mapping so that when map() is signalled from the sender, the signal mapped(object ) is emitted.
There may be at most one object for each sender.
© The Qt Company Ltd
Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-5.9/qsignalmapper.html