Class: QgsRelation¶
- class qgis.core.QgsRelation¶
Bases:
sip.wrapper
Default constructor. Creates an invalid relation.
QgsRelation(context:
QgsRelationContext
) Constructor with context. Creates an invalid relation.QgsRelation(other:
QgsRelation
) Copies a relation. This makes a shallow copy, relations are implicitly shared and only duplicated when the copy is changed.Enums
alias of
RelationshipStrength
alias of
RelationshipType
Methods
Add a field pair which is part of this relation The first element of each pair are the field names of the foreign key.
Returns a user-friendly translated string representing a relationship
cardinality
.Creates a relation from an XML structure.
Returns the field pairs which form this relation The first element of each pair are the field names of the foreign key.
Generate a (project-wide) unique id for this relation
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature.
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature.
Creates an iterator which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
Returns a filter expression which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
Creates a request to return all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
Compares the two
QgsRelation
, ignoring the name and the ID.A (project-wide) unique id for this relation
Returns the validity of this relation.
Returns a human readable name for this relation.
Returns the parent polymorphic relation.
Returns the parent polymorphic relation id.
Returns a list of attributes used to form the referenced fields (most likely primary key) on the referenced (parent) layer.
Access the referenced (parent) layer
Access the referenced (parent) layer's id
Returns a list of attributes used to form the referencing fields (foreign key) on the referencing (child) layer.
Access the referencing (child) layer This is the layer which has the field(s) which point to another layer
Access the referencing (child) layer's id This is the layer which has the field(s) which point to another layer
Gets the referenced field counterpart given a referencing field.
Gets the referencing field counterpart given a referenced field.
Set an id for this relation
Set a name for this relation
Sets the parent polymorphic relation id.
Set the referenced (parent) layer id.
Set the referencing (child) layer id.
Set a strength for this relation
Returns the relation strength as a string
Returns a user-friendly translated string representing a relationship
strength
.Returns the type of the relation
Updates the validity status of this relation.
Returns a user-friendly explanation for why the relationship is invalid.
Writes a relation to an XML structure.
Attributes
- RelationStrength¶
alias of
RelationshipStrength
- RelationType¶
alias of
RelationshipType
- addFieldPair(self, referencingField: str, referencedField: str)¶
Add a field pair which is part of this relation The first element of each pair are the field names of the foreign key. The second element of each pair are the field names of the matching primary key.
- Parameters:
referencingField (str) – The field name on the referencing (child) layer (FK)
referencedField (str) – The field name on the referenced (parent) layer (PK)
- cardinalityToDisplayString(cardinality: Qgis.RelationshipCardinality) str ¶
Returns a user-friendly translated string representing a relationship
cardinality
.New in version 3.28.
- Parameters:
cardinality (Qgis.RelationshipCardinality) –
- Return type:
str
- createFromXml(node: QDomNode, context: QgsReadWriteContext, relationContext: QgsRelationContext = QgsRelationContext()) QgsRelation ¶
Creates a relation from an XML structure. Used for reading .qgs projects.
- Parameters:
node (QDomNode) – The dom node containing the relation information
context (QgsReadWriteContext) – to pass project translator
relationContext (
QgsRelationContext
= QgsRelationContext()) – a relation context
- Return type:
- Returns:
A relation
- fieldPairs(self) Dict[str, str] ¶
Returns the field pairs which form this relation The first element of each pair are the field names of the foreign key. The second element of each pair are the field names of the matching primary key.
- Return type:
Dict[str, str]
- Returns:
The fields forming the relation
- generateId(self)¶
Generate a (project-wide) unique id for this relation
- getReferencedFeature(self, feature: QgsFeature) QgsFeature ¶
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature.
- Parameters:
feature (QgsFeature) – A feature from the referencing (child) layer
- Return type:
- Returns:
A request the referenced feature
- getReferencedFeatureRequest(self, attributes: object) QgsFeatureRequest ¶
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature.
- Parameters:
attributes (object) – An attribute vector containing the foreign key
- Returns:
A request the referenced feature
getReferencedFeatureRequest(self, feature:
QgsFeature
) -> QgsFeatureRequest Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature.- Parameters:
feature – A feature from the referencing (child) layer
- Return type:
- Returns:
A request the referenced feature
- getRelatedFeatures(self, feature: QgsFeature) QgsFeatureIterator ¶
Creates an iterator which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
- Parameters:
feature (QgsFeature) – A feature from the referenced (parent) layer
- Return type:
- Returns:
An iterator with all the referenced features
See also
See also
- getRelatedFeaturesFilter(self, feature: QgsFeature) str ¶
Returns a filter expression which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
- Parameters:
feature (QgsFeature) – A feature from the referenced (parent) layer
- Return type:
str
- Returns:
expression filter string for all the referencing features
See also
See also
- getRelatedFeaturesRequest(self, feature: QgsFeature) QgsFeatureRequest ¶
Creates a request to return all the features on the referencing (child) layer which have a foreign key pointing to the provided feature.
- Parameters:
feature (QgsFeature) – A feature from the referenced (parent) layer
- Return type:
- Returns:
A request for all the referencing features
See also
See also
- hasEqualDefinition(self, other: QgsRelation) bool ¶
Compares the two
QgsRelation
, ignoring the name and the ID.- Parameters:
other (QgsRelation) – The other relation
- Return type:
bool
- Returns:
True
if they are similar
- id(self) str ¶
A (project-wide) unique id for this relation
- Return type:
str
- Returns:
The id
- isValid(self) bool ¶
Returns the validity of this relation. Don’t use the information if it’s not valid. A relation is considered valid if both referenced and referencig layers are valid.
- Return type:
bool
- Returns:
True
if the relation is valid
See also
- name(self) str ¶
Returns a human readable name for this relation. Mostly used as title for the children.
See also
- Return type:
str
- Returns:
A name
- polymorphicRelation(self) QgsPolymorphicRelation ¶
Returns the parent polymorphic relation. If the relation is a normal relation, an invalid polymorphic relation is returned.
New in version 3.18.
- Return type:
- polymorphicRelationId(self) str ¶
Returns the parent polymorphic relation id. If the relation is a normal relation, a null string is returned.
New in version 3.18.
- Return type:
str
- referencedFields(self) List[int] ¶
Returns a list of attributes used to form the referenced fields (most likely primary key) on the referenced (parent) layer.
- Return type:
List[int]
- Returns:
A list of attributes
- referencedLayer(self) QgsVectorLayer ¶
Access the referenced (parent) layer
- Return type:
- Returns:
referenced layer
- referencedLayerId(self) str ¶
Access the referenced (parent) layer’s id
- Return type:
str
- Returns:
The id of the referenced layer
- referencingFields(self) List[int] ¶
Returns a list of attributes used to form the referencing fields (foreign key) on the referencing (child) layer.
- Return type:
List[int]
- Returns:
A list of attributes
- referencingLayer(self) QgsVectorLayer ¶
Access the referencing (child) layer This is the layer which has the field(s) which point to another layer
- Return type:
- Returns:
The referencing layer
- referencingLayerId(self) str ¶
Access the referencing (child) layer’s id This is the layer which has the field(s) which point to another layer
- Return type:
str
- Returns:
The id of the referencing layer
- resolveReferencedField(self, referencingField: str) str ¶
Gets the referenced field counterpart given a referencing field.
- Parameters:
referencingField (str) –
- Return type:
str
- resolveReferencingField(self, referencedField: str) str ¶
Gets the referencing field counterpart given a referenced field.
- Parameters:
referencedField (str) –
- Return type:
str
- setId(self, id: str)¶
Set an id for this relation
- Parameters:
id (str) –
- setName(self, name: str)¶
Set a name for this relation
- Parameters:
name (str) –
- setPolymorphicRelationId(self, polymorphicRelationId: str)¶
Sets the parent polymorphic relation id.
New in version 3.18.
- Parameters:
polymorphicRelationId (str) –
- setReferencedLayer(self, id: str)¶
Set the referenced (parent) layer id. This layer will be searched in the registry.
- Parameters:
id (str) –
- setReferencingLayer(self, id: str)¶
Set the referencing (child) layer id. This layer will be searched in the registry.
- Parameters:
id (str) –
- setStrength(self, strength: Qgis.RelationshipStrength)¶
Set a strength for this relation
- Parameters:
strength (Qgis.RelationshipStrength) –
- staticMetaObject = <PyQt5.QtCore.QMetaObject object>¶
- strength(self) Qgis.RelationshipStrength ¶
Returns the relation strength as a string
- Return type:
- Returns:
strength
- strengthToDisplayString(strength: Qgis.RelationshipStrength) str ¶
Returns a user-friendly translated string representing a relationship
strength
.New in version 3.28.
- Parameters:
strength (Qgis.RelationshipStrength) –
- Return type:
str
- type(self) Qgis.RelationshipType ¶
Returns the type of the relation
New in version 3.18.
- Return type:
- updateRelationStatus(self)¶
Updates the validity status of this relation. Will be called internally whenever a member is changed.
New in version 3.6.
- validationError(self) str ¶
Returns a user-friendly explanation for why the relationship is invalid.
Returns an empty string if the relationship
isValid()
.See also
New in version 3.28.
- Return type:
str
- writeXml(self, node: QDomNode, doc: QDomDocument)¶
Writes a relation to an XML structure. Used for saving .qgs projects
- Parameters:
node (QDomNode) – The parent node in which the relation will be created
doc (QDomDocument) – The document in which the relation will be saved