QSignalMapper

The QSignalMapper class bundles signals from identifiable senders. More

Inheritance diagram of PySide2.QtCore.QSignalMapper

Synopsis

Functions

Slots

Signals

Detailed Description

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(QWidget):
    def __init__(self, texts, parent=None):
        QWidget.__init__(self, parent)
        ...

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.

This class was mostly useful before lambda functions could be used as slots. The example above can be rewritten simpler without QSignalMapper by connecting to a lambda function.

ButtonWidget::ButtonWidget(const QStringList &texts, QWidget *parent)
    : QWidget(parent)
{
    QGridLayout *gridLayout = new QGridLayout;
    for (int i = 0; i < texts.size(); ++i) {
        QString text = texts[i];
        QPushButton *button = new QPushButton(text);
        connect(button, &QPushButton::clicked, [=] { clicked(text); });
        gridLayout->addWidget(button, i / 3, i % 3);
    }
    setLayout(gridLayout);
}
class QSignalMapper([parent=None])

Note

This constructor is deprecated.

param parent

QObject

Constructs a QSignalMapper with parent parent .

PySide2.QtCore.QSignalMapper.map(sender)
Parameters

senderQObject

This slot emits signals based on the sender object.

PySide2.QtCore.QSignalMapper.map()

This slot emits signals based on which object sends signals to it.

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1QObject

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1int

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1 – unicode

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1QWidget

PySide2.QtCore.QSignalMapper.mapping(object)
Parameters

objectQObject

Return type

QObject

This function overloads mapping() .

Returns the sender QObject that is associated with the object .

PySide2.QtCore.QSignalMapper.mapping(widget)
Parameters

widgetQWidget

Return type

QObject

This function overloads mapping() .

Returns the sender QObject that is associated with the widget .

PySide2.QtCore.QSignalMapper.mapping(text)
Parameters

text – unicode

Return type

QObject

PySide2.QtCore.QSignalMapper.mapping(id)
Parameters

idint

Return type

QObject

Returns the sender QObject that is associated with the id .

See also

setMapping()

PySide2.QtCore.QSignalMapper.removeMappings(sender)
Parameters

senderQObject

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.

PySide2.QtCore.QSignalMapper.setMapping(sender, object)
Parameters

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.

PySide2.QtCore.QSignalMapper.setMapping(sender, widget)
Parameters
  • senderQObject

  • widgetQWidget

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.

PySide2.QtCore.QSignalMapper.setMapping(sender, text)
Parameters
  • senderQObject

  • text – unicode

PySide2.QtCore.QSignalMapper.setMapping(sender, id)
Parameters

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()