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. Note that in most cases you can use lambdas for passing custom parameters to slots. This is less costly and will simplify the code.

The class supports the mapping of particular strings, integers, objects and widgets with particular objects using setMapping() . The objects’ signals can then be connected to the map() slot which will emit a signal (it could be mappedInt() , mappedString() , mappedWidget() and mappedObject() ) with a value 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, &QPushButton::clicked, signalMapper, &QSignalMapper::map);
        signalMapper->setMapping(button, texts[i]);
        gridLayout->addWidget(button, i / 3, i % 3);
    }

    connect(signalMapper, &QSignalMapper::mappedString,
            this, &ButtonWidget::clicked);

    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 mappedString() 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, [this, text] { clicked(text); });
        gridLayout->addWidget(button, i / 3, i % 3);
    }
    setLayout(gridLayout);
}

See also

QObject QButtonGroup QActionGroup

class PySide2.QtCore.QSignalMapper([parent=None])
param parent

PySide2.QtCore.QObject

Constructs a QSignalMapper with parent parent .

PySide2.QtCore.QSignalMapper.map()

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

PySide2.QtCore.QSignalMapper.map(sender)
Parameters

senderPySide2.QtCore.QObject

This slot emits signals based on the sender object.

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1 – int

Note

This function is deprecated.

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1PySide2.QtWidgets.QWidget

Note

This function is deprecated.

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1PySide2.QtCore.QObject

Note

This function is deprecated.

PySide2.QtCore.QSignalMapper.mapped(arg__1)
Parameters

arg__1 – str

Note

This function is deprecated.

PySide2.QtCore.QSignalMapper.mappedInt(arg__1)
Parameters

arg__1 – int

PySide2.QtCore.QSignalMapper.mappedObject(arg__1)
Parameters

arg__1PySide2.QtCore.QObject

PySide2.QtCore.QSignalMapper.mappedString(arg__1)
Parameters

arg__1 – str

PySide2.QtCore.QSignalMapper.mappedWidget(arg__1)
Parameters

arg__1PySide2.QtWidgets.QWidget

PySide2.QtCore.QSignalMapper.mapping(object)
Parameters

objectPySide2.QtCore.QObject

Return type

PySide2.QtCore.QObject

This function overloads mapping() .

Returns the sender QObject that is associated with the object .

PySide2.QtCore.QSignalMapper.mapping(widget)
Parameters

widgetPySide2.QtWidgets.QWidget

Return type

PySide2.QtCore.QObject

This function overloads mapping() .

Returns the sender QObject that is associated with the widget .

PySide2.QtCore.QSignalMapper.mapping(text)
Parameters

text – str

Return type

PySide2.QtCore.QObject

PySide2.QtCore.QSignalMapper.mapping(id)
Parameters

id – int

Return type

PySide2.QtCore.QObject

Returns the sender QObject that is associated with the id .

See also

setMapping()

PySide2.QtCore.QSignalMapper.removeMappings(sender)
Parameters

senderPySide2.QtCore.QObject

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 mappedObject (object ) is emitted.

There may be at most one object for each sender.

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

Adds a mapping so that when map() is signalled from the sender , the signal mappedWidget (widget ) is emitted.

There may be at most one widget for each sender.

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

Adds a mapping so that when map() is signalled from the given sender , the signal mappedInt (id ) is emitted.

There may be at most one integer ID for each sender.

See also

mapping()