Class: QgsAbstractPropertyCollection¶

Abstract base class for QgsPropertyCollection like objects.

Class Hierarchy¶

Subclasses¶

`QgsPropertyCollection`	A grouped map of multiple `QgsProperty` objects, each referenced by a integer key value.
`QgsPropertyCollectionStack`	An ordered stack of `QgsPropertyCollection` containers, where collections added later to the stack will take priority over earlier collections.

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.
`valueAsDateTime`	Calculates the current value of the property with the specified key and interprets it as a datetime.
`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

class qgis.core.QgsAbstractPropertyCollection[source]¶

Bases: object

__init__(name: str | None = '')

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

Parameters:: name (Optional[str] = '')

__init__(a0: QgsAbstractPropertyCollection)

Parameters:: a0 (QgsAbstractPropertyCollection)

clear(self)[source]¶: Removes all properties from the collection.

hasActiveProperties(self) → bool[source]¶

Returns True if the collection has any active properties, or False if all properties within the collection are deactivated.

See also

hasDynamicProperties()

Return type:: bool

hasDynamicProperties(self) → bool[source]¶

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.

See also

hasActiveProperties()

Return type:: bool

hasProperty(self, key: int) → bool[source]¶

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[source]¶

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[source]¶

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, QgsPropertyDefinition])

Return type:

bool

name(self) → str[source]¶

Returns the descriptive name of the property collection.

See also

setName()

Return type:: str

prepare(self, context: QgsExpressionContext = QgsExpressionContext()) → bool[source]¶

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[source]¶

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) → Any¶

Returns a list of property keys contained within the collection.

Return type:: Any

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

Reads property collection state from an XML element.

Parameters:

collectionElem (QDomElement) – source DOM element for property collection’s state
definitions (Dict[int, QgsPropertyDefinition]) – property definitions

See also

writeXml()

Return type:: bool

referencedFields(self, context: QgsExpressionContext = QgsExpressionContext(), ignoreContext: bool = False) → 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.
ignoreContext (bool = False) – This parameter has been added in QGIS 3.14. When set to True, even fields not set in context’s fields() will be reported - this is useful e.g. with vector tiles where the actual available field names may not be known beforehand.

Return type:

Set[str]

setName(self, name: str | None)[source]¶

Sets the descriptive name for the property collection.

See also

name()

Parameters:: name (Optional[str])

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

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, QgsPropertyDefinition])
Return type:: Any

value(self, key: int, context: QgsExpressionContext, defaultValue: Any = None) → Any[source]¶

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

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

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) -> (bool) – default boolean to return if the property cannot be calculated as a boolean

Returns:

value parsed to bool
ok: True if conversion was successful

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valueAsColor(self, key: int, context: QgsExpressionContext, defaultColor: QColor | Qt.GlobalColor = QColor())[source]¶

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, Qt.GlobalColor] = QColor()) -> (QColor) – default color to return if the property cannot be calculated as a color

Returns:

value parsed to color
ok: True if conversion was successful

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valueAsDateTime(self, key: int, context: QgsExpressionContext, defaultDateTime: QDateTime | datetime.datetime = QDateTime())[source]¶

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

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.
defaultDateTime (Union[QDateTime, datetime.datetime] = QDateTime()) -> (QDateTime) – default datetime to return if the property cannot be calculated as a datetime

Returns:

value parsed to datetime
ok: True if conversion was successful

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Added in version 3.14.

valueAsDouble(self, key: int, context: QgsExpressionContext, defaultValue: float = 0)[source]¶

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) -> (float) – default double to return if the property cannot be calculated as a double

Returns:

value parsed to double
ok: True if conversion was successful

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valueAsInt(self, key: int, context: QgsExpressionContext, defaultValue: int = 0)[source]¶

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) -> (int) – default integer to return if the property cannot be calculated as a integer

Returns:

value parsed to integer
ok: True if conversion was successful

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valueAsString(self, key: int, context: QgsExpressionContext, defaultString: str | None = '')[source]¶

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 (Optional[str] = '') -> (str) – default string to return if the property cannot be calculated as a string

Returns:

value parsed to string
ok: True if conversion was successful

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writeXml(self, collectionElem: QDomElement, definitions: Dict[int, QgsPropertyDefinition]) → bool[source]¶

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, QgsPropertyDefinition]) – property definitions

See also

readXml()

Return type:: bool