QSignalMapper

The QSignalMapper class bundles signals from identifiable senders. More

Inheritance diagram of PySide6.QtCore.QSignalMapper

Synopsis

Functions

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() 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 PySide6.QtCore.QSignalMapper([parent=None])
Parameters

parentPySide6.QtCore.QObject

Constructs a QSignalMapper with parent parent.

PySide6.QtCore.QSignalMapper.map()

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

PySide6.QtCore.QSignalMapper.map(sender)
Parameters

senderPySide6.QtCore.QObject

This slot emits signals based on the sender object.

PySide6.QtCore.QSignalMapper.mappedInt(arg__1)
Parameters

arg__1 – int

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.

See also

setMapping()

PySide6.QtCore.QSignalMapper.mappedObject(arg__1)
Parameters

arg__1PySide6.QtCore.QObject

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.

See also

setMapping()

PySide6.QtCore.QSignalMapper.mappedString(arg__1)
Parameters

arg__1 – str

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.

See also

setMapping()

PySide6.QtCore.QSignalMapper.mapping(object)
Parameters

objectPySide6.QtCore.QObject

Return type

PySide6.QtCore.QObject

This function overloads mapping() .

Returns the sender QObject that is associated with the object.

PySide6.QtCore.QSignalMapper.mapping(text)
Parameters

text – str

Return type

PySide6.QtCore.QObject

PySide6.QtCore.QSignalMapper.mapping(id)
Parameters

id – int

Return type

PySide6.QtCore.QObject

Returns the sender QObject that is associated with the id.

See also

setMapping()

PySide6.QtCore.QSignalMapper.removeMappings(sender)
Parameters

senderPySide6.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.

PySide6.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.

PySide6.QtCore.QSignalMapper.setMapping(sender, text)
Parameters
PySide6.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()