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.

Parameters

name

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.

Return type

bool

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.

Return type

bool

hasProperty(self, key: int) → bool

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

Parameters

key (int) – 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()

Return type

bool

isActive(self, key: int) → bool

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

Parameters

key (int) – 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.

Return type

bool

loadVariant(self, configuration: Any, definitions: Dict[int, QgsPropertyDefinition]) → 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()

Parameters
  • configuration (Any) –

  • definitions (Dict[int) –

Return type

bool

name(self) → str

Returns the descriptive name of the property collection.

See also

setName()

Return type

str

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.

Parameters

context (QgsExpressionContext = QgsExpressionContext()) –

Return type

bool

property(self, key: int) → QgsProperty

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

Parameters

key (int) – 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.

Return type

QgsProperty

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.

Return type

object

readXml(self, collectionElem: QDomElement, definitions: Dict[int, QgsPropertyDefinition]) → bool

Reads property collection state from an XML element.

Parameters
  • collectionElem (QDomElement) – source DOM element for property collection’s state

  • definitions (Dict[int) – property definitions

See also

writeXml()

Return type

bool

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

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

Parameters

context (QgsExpressionContext = QgsExpressionContext()) – expression context the properties will be evaluated against.

Return type

Set[str]

setName(self, name: str)

Sets the descriptive name for the property collection.

See also

name()

Parameters

name (str) –

toVariant(self, definitions: Dict[int, QgsPropertyDefinition]) → 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()

Parameters

definitions (Dict[int) –

Return type

Any

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. If you need the validity of the value (like ok provided from the valueAs* variants) refer to the property() and QgsProperty.value()

Parameters
  • key (int) – 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) – expression context to evaluate property against

  • defaultValue (Any = None) – default value to return if no matching, active property found or if the property value cannot be calculated

Return type

Any

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 (int) – 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) – QgsExpressionContext to evaluate the property for.

  • defaultValue (bool = False) – default boolean to return if the property cannot be calculated as a boolean

Return type

Tuple[bool, bool]

Returns

  • value parsed to bool

  • ok: 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 (int) – 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) – QgsExpressionContext to evaluate the property for.

  • defaultColor (Union[QColor) – default color to return if the property cannot be calculated as a color

Return type

Tuple[QColor, bool]

Returns

  • value parsed to color

  • ok: 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 (int) – 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) – QgsExpressionContext to evaluate the property for.

  • defaultValue (float = 0) – default double to return if the property cannot be calculated as a double

Return type

Tuple[float, bool]

Returns

  • value parsed to double

  • ok: 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 (int) – 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) – QgsExpressionContext to evaluate the property for.

  • defaultValue (int = 0) – default integer to return if the property cannot be calculated as a integer

Return type

Tuple[int, bool]

Returns

  • value parsed to integer

  • ok: 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 (int) – 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) – QgsExpressionContext to evaluate the property for.

  • defaultString (str = '') – default string to return if the property cannot be calculated as a string

Return type

Tuple[str, bool]

Returns

  • value parsed to string

  • ok: 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: Dict[int, QgsPropertyDefinition]) → bool

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

Parameters
  • collectionElem (QDomElement) – destination element for the property collection’s state

  • definitions (Dict[int) – property definitions

See also

readXml()

Return type

bool