class QQmlPropertyMap#

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

Synopsis#

Methods#

def __init__()
def clear()
def contains()
def count()
def freeze()
def insert()
def isEmpty()
def keys()
def operator[]()
def size()
def value()

Virtual methods#

def updateValue()

Signals#

def valueChanged()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description#

QQmlPropertyMap 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
QQmlPropertyMap ownerData;
ownerData.insert("name", QVariant(QString("John Smith")));
ownerData.insert("phone", QVariant(QString("555-5555")));

// expose it to the UI layer
QQuickView view;
QQmlContext *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.

Note

When deriving a class from QQmlPropertyMap , use the protected two-argument constructor which ensures that the class is correctly registered with the Qt Meta-Object System.

Note

The QMetaObject of a QQmlPropertyMap is dynamically generated and modified. Operations on that meta object are not thread safe, so applications need to take care to explicitly synchronize access to the meta object.

__init__([parent=None])#

Parameters:: parent – QObject

Constructs a bindable map with parent object parent.

clear(key)#

Parameters:: key – str

Clears the value (if any) associated with key.

contains(key)#

Parameters:: key – str
Return type:: bool

Returns true if the map contains key.

See also

size()

count()#

Return type:: int

This is an overloaded function.

Same as size() .

freeze()#

Disallows any further properties to be added to this property map. Existing properties can be modified or cleared.

In turn, an internal cache is turned on for the existing properties, which may result in faster access from QML.

insert(values)#

Parameters:: values – Dictionary with keys of type .QString and values of type QVariant.

Inserts the values into the QQmlPropertyMap .

Keys that don’t exist are automatically created.

This method is substantially faster than calling insert(key, value) many times in a row.

insert(key, value)

Parameters:

key – str
value – object

Sets the value associated with key to value.

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

isEmpty()#

Return type:: bool

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

See also

size()

keys()#

Return type:: list of strings

Returns the list of keys.

Keys that have been cleared will still appear in this list, even though their associated values are invalid QVariants.

operator(key)#

Parameters:: key – str
Return type:: object

This is an overloaded function.

Same as value() .

size()#

Return type:: int

Returns the number of keys in the map.

See also

isEmpty() count()

updateValue(key, input)#

Parameters:

key – str
input – object

Return type:

object

Returns the new value to be stored for the key key. This function is provided to intercept updates to a property from QML, where the value provided from QML is input.

Override this function to manipulate the property value as it is updated. Note that this function is only invoked when the value is updated from QML.

value(key)#

Parameters:: key – str
Return type:: object

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.

valueChanged(key, value)#

Parameters:

key – str
value – object

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.