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# QSignalMapper Class Reference
[QtCore module]

The QSignalMapper class bundles signals from identifiable senders. More...

Inherits QObject.

### Methods

- __init__ (self, QObject parent = None)
- map (self)
- map (self, QObject)
- QObject mapping (self, int)
- QObject mapping (self, QString)
- QObject mapping (self, QWidget)
- QObject mapping (self, QObject)
- removeMappings (self, QObject)
- setMapping (self, QObject, int)
- setMapping (self, QObject, QString)
- setMapping (self, QObject, QWidget)
- setMapping (self, QObject, QObject)

### Qt Signals

- void mapped (int)
- void mapped (const QString&)
- void mapped (QWidget *)
- void mapped (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(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(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(const QString &)),
                 this, SIGNAL(clicked(const 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.

## Method Documentation

### QSignalMapper.__init__ (self, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QSignalMapper with parent parent.

### QSignalMapper.map (self)

This method is also a Qt slot with the C++ signature `void map()`.

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

### QSignalMapper.map (self, QObject)

This method is also a Qt slot with the C++ signature `void map(QObject *)`.

This slot emits signals based on the sender object.

### QObject QSignalMapper.mapping (self, int)

Returns the sender QObject that is associated with the id.

See also setMapping().

### QObject QSignalMapper.mapping (self, QString)

This function overloads mapping().

### QObject QSignalMapper.mapping (self, QWidget)

This function overloads mapping().

Returns the sender QObject that is associated with the widget.

### QObject QSignalMapper.mapping (self, QObject)

This function overloads mapping().

Returns the sender QObject that is associated with the object.

### QSignalMapper.removeMappings (self, QObject)

Removes all mappings for sender.

This is done automatically when mapped objects are destroyed.

### QSignalMapper.setMapping (self, QObject, int)

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().

### QSignalMapper.setMapping (self, QObject, QString)

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.

### QSignalMapper.setMapping (self, QObject, QWidget)

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.

### QSignalMapper.setMapping (self, QObject, QObject)

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.

## Qt Signal Documentation

### void mapped (int)

This is the default overload of this signal.

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().

### void mapped (const QString&)

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().

### void mapped (QWidget *)

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.

See also setMapping().

### void mapped (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().