Class: QgsRelationManager¶

This class manages a set of relations between layers.

Class Hierarchy¶

Base classes¶

Methods

`addPolymorphicRelation`	Adds a new polymorphic relation.
`addRelation`	Add a relation.
`clear`	Remove any relation managed by this class.
`context`	Gets the relation context
`polymorphicRelation`	Returns the list of relations associated with a polymorphic relation
`polymorphicRelations`	Returns all the polymorphic relations
`referencedRelations`	Gets all relations where this layer is the referenced part (i.e. the parent table with the primary key being referenced from another layer).
`referencingRelations`	Gets all relations where the specified layer (and field) is the referencing part (i.e. the child table with the foreign key).
`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.
`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.
`updateRelationsStatus`	Updates relations status

Static Methods

discoverRelations

Discover all the relations available from the current layers.

Signals

`changed`	Emitted when relations are added or removed to the manager.
`relationsLoaded`	Emitted when the relations were loaded after reading a project

class qgis.core.QgsRelationManager[source]¶

Bases: QObject

__init__(project: QgsProject | None = None)

Constructor for QgsRelationManager.

Parameters:: project (Optional[QgsProject] = None) – associated project (used to notify project of changes)

addPolymorphicRelation(self, polymorphicRelation: QgsPolymorphicRelation)[source]¶

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

Parameters:: polymorphicRelation (QgsPolymorphicRelation)

addRelation(self, relation: QgsRelation)[source]¶

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

Parameters:: relation (QgsRelation) – The relation to add.

signal changed[source]¶: Emitted when relations are added or removed to the manager.

clear(self)[source]¶: Remove any relation managed by this class.

context(self) → QgsRelationContext[source]¶

Gets the relation context

Return type:: QgsRelationContext

static 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

polymorphicRelation(self, polymorphicRelationId: str | None) → QgsPolymorphicRelation[source]¶

Returns the list of relations associated with a polymorphic relation

Parameters:: polymorphicRelationId (Optional[str])
Return type:: QgsPolymorphicRelation

polymorphicRelations(self) → Dict[str, QgsPolymorphicRelation]¶

Returns all the polymorphic relations

Return type:: Dict[str, QgsPolymorphicRelation]

referencedRelations(self, layer: QgsVectorLayer | None = 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 (Optional[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 = 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 (Optional[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 | None) → QgsRelation[source]¶

Gets access to a relation by its id.

Parameters:: id (Optional[str]) – The id to search for
Return type:: QgsRelation
Returns:: A relation. Invalid if not found.