Subgroup: Relation
Class: QgsRelation¶
-
class
qgis.core.
QgsRelation
¶ Bases:
sip.wrapper
Default constructor. Creates an invalid relation.
QgsRelation(QgsRelation)
Methods
addFieldPair
Add a field pairs which is part of this relation The first element of each pair are the field names of the foreign key. createFromXml
Creates a relation from an XML structure. fieldPairs
Returns the field pairs which form this relation The first element of each pair are the field names of the foreign key. generateId
Generate a (project-wide) unique id for this relation getReferencedFeature
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature. getReferencedFeatureRequest
Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature. getRelatedFeatures
Creates an iterator which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. getRelatedFeaturesFilter
Returns a filter expression which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. getRelatedFeaturesRequest
Creates a request to return all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. hasEqualDefinition
Compares the two QgsRelation, ignoring the name and the ID. id
A (project-wide) unique id for this relation isValid
Returns the validity of this relation. name
Returns a human readable name for this relation. referencedFields
Returns a list of attributes used to form the referenced fields (most likely primary key) on the referenced (parent) layer. referencedLayer
Access the referenced (parent) layer referencedLayerId
Access the referenced (parent) layer’s id referencingFields
Returns a list of attributes used to form the referencing fields (foreign key) on the referencing (child) layer. referencingLayer
Access the referencing (child) layer referencingLayerId
Access the referencing (child) layer’s id resolveReferencedField
Get the referenced field counterpart given a referencing field. resolveReferencingField
Get the referencing field counterpart given a referenced field. setId
Set an id for this relation setName
Set a name for this relation setReferencedLayer
Set the referenced (parent) layer id. setReferencingLayer
Set the referencing (child) layer id. setStrength
Set a strength for this relation strength
Returns the relation strength as a string writeXml
Writes a relation to an XML structure. Attributes
Association
Composition
-
Association
= 0¶
-
Composition
= 1¶
-
class
RelationStrength
¶ Bases:
int
-
addFieldPair
(self, referencingField: str, referencedField: str)¶ Add a field pairs 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 – The field name on the referencing (child) layer (FK)
- referencedField – The field name on the referenced (parent) layer (PK)
-
createFromXml
(node: QDomNode) → QgsRelation¶ Creates a relation from an XML structure. Used for reading .qgs projects.
Parameters: node – The dom node containing the relation information 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.
Returns: The fields forming the relation
-
generateId
(self)¶ Generate a (project-wide) unique id for this relation
New in version 3.0.
-
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 – A feature from the referencing (child) layer 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 – An attribute vector containing the foreign key Returns: A request the referenced feature Note
not available in Python bindings
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 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 – A feature from the referenced (parent) layer 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 – A feature from the referenced (parent) layer Returns: expression filter string for all the referencing features New in version 2.16.
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 – A feature from the referenced (parent) layer 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 – The other relation Returns: true if they are similar New in version 3.0.
-
id
(self) → str¶ A (project-wide) unique id for this relation
Returns: The id
-
isValid
(self) → bool¶ Returns the validity of this relation. Don’t use the information if it’s not valid.
Returns: true if the relation is valid
-
name
(self) → str¶ Returns a human readable name for this relation. Mostly used as title for the children.
See also
Returns: A name
-
referencedFields
(self) → List[int]¶ Returns a list of attributes used to form the referenced fields (most likely primary key) on the referenced (parent) layer.
Returns: A list of attributes
-
referencedLayer
(self) → QgsVectorLayer¶ Access the referenced (parent) layer
Returns: referenced layer
-
referencedLayerId
(self) → str¶ Access the referenced (parent) layer’s id
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.
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
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
Returns: The id of the referencing layer
-
resolveReferencedField
(self, referencingField: str) → str¶ Get the referenced field counterpart given a referencing field.
New in version 3.0.
-
resolveReferencingField
(self, referencedField: str) → str¶ Get the referencing field counterpart given a referenced field.
New in version 3.0.
-
setId
(self, id: str)¶ Set an id for this relation
-
setName
(self, name: str)¶ Set a name for this relation
-
setReferencedLayer
(self, id: str)¶ Set the referenced (parent) layer id. This layer will be searched in the registry.
-
setReferencingLayer
(self, id: str)¶ Set the referencing (child) layer id. This layer will be searched in the registry.
-
setStrength
(self, strength: QgsRelation.RelationStrength)¶ Set a strength for this relation
New in version 3.0.
-
strength
(self) → QgsRelation.RelationStrength¶ Returns the relation strength as a string
Returns: strength New in version 3.0.
-
writeXml
(self, node: QDomNode, doc: QDomDocument)¶ Writes a relation to an XML structure. Used for saving .qgs projects
Parameters: - node – The parent node in which the relation will be created
- doc – The document in which the relation will be saved
-