Class: QgsAbstractPropertyCollection

class qgis.core.QgsAbstractPropertyCollection(name: str = '')

Bases: sip.wrapper

Constructor for QgsAbstractPropertyCollection. The name parameter should be set to a descriptive name for the collection.

QgsAbstractPropertyCollection(QgsAbstractPropertyCollection)

Abstract base class for QgsPropertyCollection like objects.

New in version 3.0: Methods

clear Removes all properties from the collection.
hasActiveProperties Returns true if the collection has any active properties, or false if all properties within the collection are deactivated.
hasDynamicProperties Returns true if the collection has any active, non-static properties, or false if either all non-static properties within the collection are deactivated or if the collection only contains static properties.
hasProperty Returns true if the collection contains a property with the specified key.
isActive Returns true if the collection contains an active property with the specified key.
loadVariant Loads this property collection from a QVariantMap, wrapped in a QVariant.
name Returns the descriptive name of the property collection.
prepare Prepares the collection against a specified expression context.
property Returns a matching property from the collection, if one exists.
propertyKeys Returns a list of property keys contained within the collection.
readXml Reads property collection state from an XML element.
referencedFields Returns the set of any fields referenced by the active properties from the collection.
setName Sets the descriptive name for the property collection.
toVariant Saves this property collection to a QVariantMap, wrapped in a QVariant.
value Returns the calculated value of the property with the specified key from within the collection.
valueAsBool Calculates the current value of the property with the specified key and interprets it as an boolean.
valueAsColor Calculates the current value of the property with the specified key and interprets it as a color.
valueAsDouble Calculates the current value of the property with the specified key and interprets it as a double.
valueAsInt Calculates the current value of the property with the specified key and interprets it as an integer.
valueAsString Calculates the current value of the property with the specified key and interprets it as a string.
writeXml Writes the current state of the property collection into an XML element

Signals

Attributes

clear(self)

Removes all properties from the collection.

hasActiveProperties(self) → bool

Returns true if the collection has any active properties, or false if all properties within the collection are deactivated.

hasDynamicProperties(self) → bool

Returns true if the collection has any active, non-static properties, or false if either all non-static properties within the collection are deactivated or if the collection only contains static properties.

hasProperty(self, key: int) → bool

Returns true if the collection contains a property with the specified key.

Parameters:key – integer key for property. The intended use case is that a context specific enum is cast to int and used for the key value.

See also

property()

isActive(self, key: int) → bool

Returns true if the collection contains an active property with the specified key.

Parameters:key – integer key for property to test. The intended use case is that a context specific enum is cast to int and used for the key value.
loadVariant(self, configuration: Any, definitions: object) → bool

Loads this property collection from a QVariantMap, wrapped in a QVariant. You can use QgsXmlUtils.readVariant to save it to an XML document.

See also

toVariant()

name(self) → str

Returns the descriptive name of the property collection.

See also

setName()

prepare(self, context: QgsExpressionContext = QgsExpressionContext()) → bool

Prepares the collection against a specified expression context. Calling prepare before evaluating the collection’s properties multiple times allows precalculation of expensive setup tasks such as parsing expressions. Returns true if preparation was successful.

property(self, key: int) → QgsProperty

Returns a matching property from the collection, if one exists.

Parameters:key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
Returns:matching property, or null if no matching, active property found.

See also

hasProperty()

propertyKeys(self) → object

Returns a list of property keys contained within the collection.

readXml(self, collectionElem: QDomElement, definitions: object) → bool

Reads property collection state from an XML element.

Parameters:
  • collectionElem – source DOM element for property collection’s state
  • definitions – property definitions

See also

writeXml()

referencedFields(self, context: QgsExpressionContext = QgsExpressionContext()) → Set[str]

Returns the set of any fields referenced by the active properties from the collection.

Parameters:context – expression context the properties will be evaluated against.
setName(self, name: str)

Sets the descriptive name for the property collection.

See also

name()

toVariant(self, definitions: object) → Any

Saves this property collection to a QVariantMap, wrapped in a QVariant. You can use QgsXmlUtils.writeVariant to save it to an XML document.

See also

loadVariant()

value(self, key: int, context: QgsExpressionContext, defaultValue: Any = None) → Any

Returns the calculated value of the property with the specified key from within the collection.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – expression context to evaluate property against
  • defaultValue – default value to return if no matching, active property found or if the property value cannot be calculated
Returns:

calculated property value, or default value if property could not be evaluated

See also

valueAsString()

See also

valueAsColor()

See also

valueAsDouble()

See also

valueAsInt()

See also

valueAsBool()

valueAsBool(self, key: int, context: QgsExpressionContext, defaultValue: bool = False) → Tuple[bool, bool]

Calculates the current value of the property with the specified key and interprets it as an boolean.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – QgsExpressionContext to evaluate the property for.
  • defaultValue – default boolean to return if the property cannot be calculated as a boolean
Returns:

  • value parsed to bool
  • ok: if specified, will be set to true if conversion was successful

See also

value()

See also

valueAsString()

See also

valueAsColor()

See also

valueAsDouble()

See also

valueAsInt()

valueAsColor(self, key: int, context: QgsExpressionContext, defaultColor: Union[QColor, Qt.GlobalColor, QGradient] = QColor()) → Tuple[QColor, bool]

Calculates the current value of the property with the specified key and interprets it as a color.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – QgsExpressionContext to evaluate the property for.
  • defaultColor – default color to return if the property cannot be calculated as a color
Returns:

  • value parsed to color
  • ok: if specified, will be set to true if conversion was successful

See also

value()

See also

valueAsString()

See also

valueAsDouble()

See also

valueAsInt()

See also

valueAsBool()

valueAsDouble(self, key: int, context: QgsExpressionContext, defaultValue: float = 0) → Tuple[float, bool]

Calculates the current value of the property with the specified key and interprets it as a double.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – QgsExpressionContext to evaluate the property for.
  • defaultValue – default double to return if the property cannot be calculated as a double
Returns:

  • value parsed to double
  • ok: if specified, will be set to true if conversion was successful

See also

value()

See also

valueAsString()

See also

valueAsColor()

See also

valueAsInt()

See also

valueAsBool()

valueAsInt(self, key: int, context: QgsExpressionContext, defaultValue: int = 0) → Tuple[int, bool]

Calculates the current value of the property with the specified key and interprets it as an integer.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – QgsExpressionContext to evaluate the property for.
  • defaultValue – default integer to return if the property cannot be calculated as a integer
Returns:

  • value parsed to integer
  • ok: if specified, will be set to true if conversion was successful

See also

value()

See also

valueAsString()

See also

valueAsColor()

See also

valueAsDouble()

See also

valueAsBool()

valueAsString(self, key: int, context: QgsExpressionContext, defaultString: str = '') → Tuple[str, bool]

Calculates the current value of the property with the specified key and interprets it as a string.

Parameters:
  • key – integer key for property to return. The intended use case is that a context specific enum is cast to int and used for the key value.
  • context – QgsExpressionContext to evaluate the property for.
  • defaultString – default string to return if the property cannot be calculated as a string
Returns:

  • value parsed to string
  • ok: if specified, will be set to true if conversion was successful

See also

value()

See also

valueAsColor()

See also

valueAsDouble()

See also

valueAsInt()

See also

valueAsBool()

writeXml(self, collectionElem: QDomElement, definitions: object) → bool

Writes the current state of the property collection into an XML element

Parameters:
  • collectionElem – destination element for the property collection’s state
  • definitions – property definitions

See also

readXml()