Class: QgsValueRelationFieldFormatter

class qgis.core.QgsValueRelationFieldFormatter

Bases: qgis._core.QgsFieldFormatter

Constructor for QgsValueRelationFieldFormatter.

QgsValueRelationFieldFormatter(QgsValueRelationFieldFormatter)

Field formatter for a value relation field. A value relation field formatter looks up the values from features on another layer.

New in version 3.0: Methods

createCache createCache(config: Dict[str, Any], formFeature: QgsFeature = QgsFeature()) -> object Create a cache for a value relation field.
expressionFormAttributes Returns a list of attributes required by the form context expression
expressionFormVariables Returns a list of variables required by the form context expression
expressionIsUsable Check whether the feature has all values required by the expression
expressionRequiresFormScope Check if the expression requires a form scope (i.e.
id
representValue
sortValue
valueToStringList Utility to convert an array or a string representation of an array value to a string list

Signals

Attributes

class ValueRelationItem(key: Any, value: str)

Bases: sip.wrapper

Constructor for ValueRelationItem

QgsValueRelationFieldFormatter.ValueRelationItem() Constructor for ValueRelationItem

QgsValueRelationFieldFormatter.ValueRelationItem(QgsValueRelationFieldFormatter.ValueRelationItem)

key
value
createCache(self, layer: QgsVectorLayer, fieldIndex: int, config: Dict[str, Any]) → Any

createCache(config: Dict[str, Any], formFeature: QgsFeature = QgsFeature()) -> object Create a cache for a value relation field. This can be used to keep the value map in the local memory if doing multiple lookups in a loop.

Parameters:
  • config – The widget configuration
  • formFeature – The feature currently being edited with current attribute values
Returns:

A kvp list of values for the widget

New in version 3.0.

expressionFormAttributes(expression: str) → Set[str]

Returns a list of attributes required by the form context expression

Parameters:expression – Form filter expression
Returns:list of attributes required by the expression

New in version 3.2.

expressionFormVariables(expression: str) → Set[str]

Returns a list of variables required by the form context expression

Parameters:expression – Form filter expression
Returns:list of variables required by the expression

New in version 3.2.

expressionIsUsable(expression: str, feature: QgsFeature) → bool

Check whether the feature has all values required by the expression

Returns:True if the expression can be used

New in version 3.2.

expressionRequiresFormScope(expression: str) → bool

Check if the expression requires a form scope (i.e. if it uses fields or geometry of the currently edited feature).

Parameters:expression – The widget’s filter expression
Returns:true if the expression requires a form scope

New in version 3.2.

id(self) → str
representValue(self, layer: QgsVectorLayer, fieldIndex: int, config: Dict[str, Any], cache: Any, value: Any) → str
sortValue(self, layer: QgsVectorLayer, fieldIndex: int, config: Dict[str, Any], cache: Any, value: Any) → Any
valueToStringList(value: Any) → List[str]

Utility to convert an array or a string representation of an array value to a string list

New in version 3.2.