Class: QgsValueRelationFieldFormatter¶

Field formatter for a value relation field.

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

Class Hierarchy¶

Base classes¶

QgsFieldFormatter

A field formatter helps to handle and display values for a field.

Virtual Methods

In PyQGIS, only methods marked as virtual can be safely overridden in a Python subclass of QgsValueRelationFieldFormatter. See the FAQ for more details.

createCache

Static Methods

`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, optionally checks for parentFeature
`expressionParentFormAttributes`	Returns a list of attributes required by the parent form's form context expression
`expressionParentFormVariables`	Returns a list of variables required by the parent form's form context expression
`expressionRequiresFormScope`	Check if the expression requires a form scope (i.e. if it uses fields or geometry of the currently edited feature).
`expressionRequiresParentFormScope`	Check if the expression requires a parent form scope (i.e. if it uses fields or geometry of the parent form's currently edited feature).
`resolveLayer`	Returns the (possibly `None`) layer from the widget's config and project
`valueToStringList`	Utility to convert a list or a string representation of an (hstore style: {1,2...}) list in value to a string list

class qgis.core.QgsValueRelationFieldFormatter[source]¶

Bases: QgsFieldFormatter

__init__(): Constructor for QgsValueRelationFieldFormatter.

__init__(a0: QgsValueRelationFieldFormatter)

Parameters:: a0 (QgsValueRelationFieldFormatter)

class ValueRelationItem(key: Any, value: str | None, description: str | None = '', group: Any = None)¶

Bases: object

Constructor for ValueRelationItem

QgsValueRelationFieldFormatter.ValueRelationItem()

QgsValueRelationFieldFormatter.ValueRelationItem(a0: QgsValueRelationFieldFormatter.ValueRelationItem)

description¶

group: object¶: Value used to regroup items during sorting (since QGIS 3.38)

key¶

value¶

virtual createCache(self, layer: QgsVectorLayer | None, fieldIndex: int, config: Dict[str, Any]) → Any[source]¶

Parameters:

layer (Optional[QgsVectorLayer])
fieldIndex (int)
config (Dict[str, Any])

Return type:

Any

virtual createCache(config: Dict[str, Any], formFeature: QgsFeature = QgsFeature(), parentFormFeature: QgsFeature = QgsFeature()) → List[QgsValueRelationFieldFormatter.ValueRelationItem][source]

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 (Dict[str, Any]) – The widget configuration
formFeature (QgsFeature = QgsFeature()) – The feature currently being edited with current attribute values
parentFormFeature (QgsFeature = QgsFeature()) – For embedded forms only, the feature currently being edited in the parent form with current attribute values

Return type:

List[QgsValueRelationFieldFormatter.ValueRelationItem]

Returns:

A kvp list of values for the widget

static expressionFormAttributes(expression: str | None) → Set[str]¶

Returns a list of attributes required by the form context expression

Parameters:: expression (Optional[str]) – Form filter expression
Return type:: Set[str]
Returns:: list of attributes required by the expression

Added in version 3.2.

static expressionFormVariables(expression: str | None) → Set[str]¶

Returns a list of variables required by the form context expression

Parameters:: expression (Optional[str]) – Form filter expression
Return type:: Set[str]
Returns:: list of variables required by the expression

Added in version 3.2.

static expressionIsUsable(expression: str | None, feature: QgsFeature, parentFeature: QgsFeature = QgsFeature()) → bool[source]¶

Check whether the feature has all values required by the expression, optionally checks for parentFeature

Return type:: bool
Returns:: True if the expression can be used

Added in version 3.2.

Parameters:

expression (Optional[str])
feature (QgsFeature)
parentFeature (QgsFeature = QgsFeature())

static expressionParentFormAttributes(expression: str | None) → Set[str]¶

Returns a list of attributes required by the parent form’s form context expression

Parameters:: expression (Optional[str]) – Form filter expression
Return type:: Set[str]
Returns:: list of parent attributes required by the expression

Added in version 3.14.

static expressionParentFormVariables(expression: str | None) → Set[str]¶

Returns a list of variables required by the parent form’s form context expression

Parameters:: expression (Optional[str]) – Form filter expression
Return type:: Set[str]
Returns:: list of parent variables required by the expression

Added in version 3.14.

static expressionRequiresFormScope(expression: str | None) → bool[source]¶

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

Parameters:: expression (Optional[str]) – The widget’s filter expression
Return type:: bool
Returns:: True if the expression requires a form scope

Added in version 3.2.

static expressionRequiresParentFormScope(expression: str | None) → bool[source]¶

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

Parameters:: expression (Optional[str]) – The widget’s filter expression
Return type:: bool
Returns:: True if the expression requires a parent form scope

Added in version 3.14.

static resolveLayer(config: Dict[str, Any], project: QgsProject | None) → QgsVectorLayer | None[source]¶

Returns the (possibly None) layer from the widget’s config and project

Added in version 3.8.

Parameters:

config (Dict[str, Any])
project (Optional[QgsProject])

Return type:

Optional[QgsVectorLayer]

static valueToStringList(value: Any) → List[str][source]¶

Utility to convert a list or a string representation of an (hstore style: {1,2…}) list in value to a string list

Added in version 3.2.

Parameters:: value (Any)
Return type:: List[str]