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# QDeclarativePropertyMap Class Reference
[QtDeclarative module]

The QDeclarativePropertyMap class allows you to set key-value pairs that can be used in QML bindings. More...

Inherits QObject.

### Methods

- __init__ (self, QObject parent = None)
- clear (self, QString key)
- bool contains (self, QString key)
- int count (self)
- insert (self, QString key, QVariant value)
- bool isEmpty (self)
- QStringList keys (self)
- int size (self)
- QVariant value (self, QString key)

### Special Methods

- QVariant __getitem__ (self, QString key)
- __len__ (self)

### Qt Signals

- void valueChanged (const QString&,const QVariant&)

## Detailed Description

The QDeclarativePropertyMap class allows you to set key-value pairs that can be used in QML bindings.

QDeclarativePropertyMap provides a convenient way to expose domain data to the UI layer. The following example shows how you might declare data in C++ and then access it in QML.

In the C++ file:

     // create our data
     QDeclarativePropertyMap ownerData;
     ownerData.insert("name", QVariant(QString("John Smith")));
     ownerData.insert("phone", QVariant(QString("555-5555")));

     // expose it to the UI layer
     QDeclarativeView view;
     QDeclarativeContext *ctxt = view.rootContext();
     ctxt->setContextProperty("owner", &ownerData);

     view.setSource(QUrl.fromLocalFile("main.qml"));
     view.show();

Then, in `main.qml`:

     Text { text: owner.name + " " + owner.phone }

The binding is dynamic - whenever a key's value is updated, anything bound to that key will be updated as well.

To detect value changes made in the UI layer you can connect to the valueChanged() signal. However, note that valueChanged() is NOT emitted when changes are made by calling insert() or clear() - it is only emitted when a value is updated from QML.

Note: It is not possible to remove keys from the map; once a key has been added, you can only modify or clear its associated value.

## Method Documentation

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

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

Constructs a bindable map with parent object parent.

### QDeclarativePropertyMap.clear (self, QString key)

Clears the value (if any) associated with key.

### bool QDeclarativePropertyMap.contains (self, QString key)

Returns true if the map contains key.

See also size().

### int QDeclarativePropertyMap.count (self)

This is an overloaded function.

Same as size().

### QDeclarativePropertyMap.insert (self, QString key, QVariant value)

Sets the value associated with key to value.

If the key doesn't exist, it is automatically created.

### bool QDeclarativePropertyMap.isEmpty (self)

Returns true if the map contains no keys; otherwise returns false.

See also size().

### QStringList QDeclarativePropertyMap.keys (self)

### int QDeclarativePropertyMap.size (self)

Returns the number of keys in the map.

See also isEmpty() and count().

### QVariant QDeclarativePropertyMap.value (self, QString key)

Returns the value associated with key.

If no value has been set for this key (or if the value has been cleared), an invalid QVariant is returned.

### QVariant QDeclarativePropertyMap.__getitem__ (self, QString key)

### QDeclarativePropertyMap.__len__ (self)

## Qt Signal Documentation

### void valueChanged (const QString&,const QVariant&)

This is the default overload of this signal.

This signal is emitted whenever one of the values in the map is changed. key is the key corresponding to the value that was changed.

Note: valueChanged() is NOT emitted when changes are made by calling insert() or clear() - it is only emitted when a value is updated from QML.