Class: QgsRelationManager

class qgis.core.QgsRelationManager

Bases: PyQt5.QtCore.QObject

This class manages a set of relations between layers.

QgsRelationManager(project: QgsProject = None) Constructor for QgsRelationManager.

Parameters

project

associated project (used to notify project of changes)

Methods

addPolymorphicRelation

Adds a new polymorphic relation.

addRelation

Add a relation.

childEvent

clear

Remove any relation managed by this class.

connectNotify

context

Gets the relation context

customEvent

disconnectNotify

discoverRelations

Discover all the relations available from the current layers.

isSignalConnected

polymorphicRelation

Returns the list of relations associated with a polymorphic relation

polymorphicRelations

Returns all the polymorphic relations

receivers

referencedRelations

Gets all relations where this layer is the referenced part (i.e.

referencingRelations

Gets all relations where the specified layer (and field) is the referencing part (i.e.

relation

Gets access to a relation by its id.

relations

Gets access to the relations managed by this class.

relationsByName

Returns a list of relations with matching names.

removePolymorphicRelation

Removes an existing polymorphic relation and it's generated relations.

removeRelation

Remove a relation.

sender

senderSignalIndex

setPolymorphicRelations

Sets the specified polymorphic relations and removes any polymorphic relations currently set.

setRelations

Will set the specified relations and remove any relation currently set.

timerEvent

updateRelationsStatus

Updates relations status

Signals

changed

Emitted when relations are added or removed to the manager.

relationsLoaded

Emitted when the relations were loaded after reading a project [signal]

addPolymorphicRelation(self, polymorphicRelation: QgsPolymorphicRelation)

Adds a new polymorphic relation. The generated relations are not available, they will be created automatically.

Parameters

polymorphicRelation (QgsPolymorphicRelation) –

addRelation(self, relation: QgsRelation)

Add a relation. Invalid relations are added only if both referencing layer and referenced layer exist.

Parameters

relation (QgsRelation) – The relation to add.

changed

Emitted when relations are added or removed to the manager.

New in version 2.5: [signal]

childEvent(self, QChildEvent)
clear(self)

Remove any relation managed by this class.

connectNotify(self, QMetaMethod)
context(self) QgsRelationContext

Gets the relation context

Return type

QgsRelationContext

customEvent(self, QEvent)
disconnectNotify(self, QMetaMethod)
discoverRelations(existingRelations: Iterable[QgsRelation], layers: Iterable[QgsVectorLayer]) List[QgsRelation]

Discover all the relations available from the current layers.

Parameters
  • existingRelations (Iterable[QgsRelation]) – the existing relations to filter them out

  • layers (Iterable[QgsVectorLayer]) – the current layers

Return type

List[QgsRelation]

Returns

the list of discovered relations

New in version 3.0.

isSignalConnected(self, QMetaMethod) bool
polymorphicRelation(self, polymorphicRelationId: str) QgsPolymorphicRelation

Returns the list of relations associated with a polymorphic relation

Parameters

polymorphicRelationId (str) –

Return type

QgsPolymorphicRelation

polymorphicRelations(self) Dict[str, QgsPolymorphicRelation]

Returns all the polymorphic relations

Return type

Dict[str, QgsPolymorphicRelation]

receivers(self, PYQT_SIGNAL) int
referencedRelations(self, layer: QgsVectorLayer = None) List[QgsRelation]

Gets all relations where this layer is the referenced part (i.e. the parent table with the primary key being referenced from another layer).

Parameters

layer (QgsVectorLayer = None) – The layer which should be searched for.

Return type

List[QgsRelation]

Returns

A list of relations where the specified layer is the referenced part.

referencingRelations(self, layer: QgsVectorLayer = None, fieldIdx: int = -2) List[QgsRelation]

Gets all relations where the specified layer (and field) is the referencing part (i.e. the child table with the foreign key).

Parameters
  • layer (QgsVectorLayer = None) – The layer which should be searched for.

  • fieldIdx (int = -2) – The field which should be part of the foreign key. If not set will return all relations.

Return type

List[QgsRelation]

Returns

A list of relations matching the given layer and fieldIdx.

relation(self, id: str) QgsRelation

Gets access to a relation by its id.

Parameters

id (str) – The id to search for

Return type

QgsRelation

Returns

A relation. Invalid if not found.

relations(self) Dict[str, QgsRelation]

Gets access to the relations managed by this class.

Return type

Dict[str, QgsRelation]

Returns

A QMap where the key is the relation id, the value the relation object.

relationsByName(self, name: str) List[QgsRelation]

Returns a list of relations with matching names.

Parameters

name (str) – relation name to search for. Searching is case insensitive.

Return type

List[QgsRelation]

Returns

a list of matching relations

See also

relation()

New in version 2.16.

relationsLoaded

Emitted when the relations were loaded after reading a project [signal]

removePolymorphicRelation(self, polymorphicRelationId: str)

Removes an existing polymorphic relation and it’s generated relations.

Parameters

polymorphicRelationId (str) –

removeRelation(self, id: str)

Remove a relation.

Parameters

id (str) – The id of the relation to remove.

removeRelation(self, relation: QgsRelation) Remove a relation.

Parameters

relation – The relation to remove.

sender(self) QObject
senderSignalIndex(self) int
setPolymorphicRelations(self, relations: Iterable[QgsPolymorphicRelation])

Sets the specified polymorphic relations and removes any polymorphic relations currently set. Will remove any generated relations and recreate them.

Parameters

relations (Iterable[QgsPolymorphicRelation]) –

setRelations(self, relations: Iterable[QgsRelation])

Will set the specified relations and remove any relation currently set.

Parameters

relations (Iterable[QgsRelation]) – A list of relations to set.

timerEvent(self, QTimerEvent)
updateRelationsStatus(self)

Updates relations status