The QgsWeakRelation class represent a QgsRelation with possibly unresolved layers or unmatched fields. More...

#include <qgsweakrelation.h>

Public Types
enum	WeakRelationType { Referencing , Referenced }
	Enum to distinguish if the layer is referenced or referencing. More...

Public Member Functions
	QgsWeakRelation ()
	Default constructor for an invalid relation.

	QgsWeakRelation (const QString &relationId, const QString &relationName, const Qgis::RelationshipStrength strength, const QString &referencingLayerId, const QString &referencingLayerName, const QString &referencingLayerSource, const QString &referencingLayerProviderKey, const QString &referencedLayerId, const QString &referencedLayerName, const QString &referencedLayerSource, const QString &referencedLayerProviderKey)
	Creates a QgsWeakRelation.

QString	backwardPathLabel () const
	Returns the label of the backward path for the relationship.

Qgis::RelationshipCardinality	cardinality () const
	Returns the relationship's cardinality.

QString	forwardPathLabel () const
	Returns the label of the forward path for the relationship.

QString	id () const
	Returns the relationship's ID.

QStringList	mappingReferencedLayerFields () const
	Returns the list of fields from the mappingTable() involved in the relationship.

QStringList	mappingReferencingLayerFields () const
	Returns the list of fields from the mappingTable() involved in the relationship.

QgsVectorLayerRef	mappingTable () const
	Returns a weak reference to the mapping table, which forms the middle table in many-to-many relationships.

QString	mappingTableName () const
	Returns the layer name of the mapping table, which forms the middle table in many-to-many relationships.

QString	mappingTableProvider () const
	Returns the provider ID for the mapping table, which forms the middle table in many-to-many relationships.

QString	mappingTableSource () const
	Returns the source URI for the mapping table, which forms the middle table in many-to-many relationships.

QString	name () const
	Returns the relationship's name.

QgsVectorLayerRef	referencedLayer () const
	Returns a weak reference to the referenced (or "parent" / "left") layer.

QStringList	referencedLayerFields () const
	Returns the list of fields from the referencedLayer() involved in the relationship.

QString	referencedLayerName () const
	Returns the layer name of the referenced (or "parent" / "left") layer.

QString	referencedLayerProvider () const
	Returns the provider ID for the referenced (or "parent" / "left") layer.

QString	referencedLayerSource () const
	Returns the source URI for the referenced (or "parent" / "left") layer.

QgsVectorLayerRef	referencingLayer () const
	Returns a weak reference to the referencing (or "child" / "right") layer.

QStringList	referencingLayerFields () const
	Returns the list of fields from the referencingLayer() involved in the relationship.

QString	referencingLayerName () const
	Returns the layer name of the referencing (or "child" / "right") layer.

QString	referencingLayerProvider () const
	Returns the provider ID for the referencing (or "child" / "right") layer.

QString	referencingLayerSource () const
	Returns the source URI for the referencing (or "child" / "right") layer.

QString	relatedTableType () const
	Returns the type string of the related table.

QList< QgsRelation >	resolvedRelations (const QgsProject *project, QgsVectorLayerRef::MatchType matchType=QgsVectorLayerRef::MatchType::All) const
	Resolves a weak relation in the given project returning a list of possibly invalid QgsRelations and without performing any kind of validity check.

void	setBackwardPathLabel (const QString &label)
	Sets the label of the backward path for the relationship.

void	setCardinality (Qgis::RelationshipCardinality cardinality)
	Sets the relationship's cardinality.

void	setForwardPathLabel (const QString &label)
	Sets the label of the forward path for the relationship.

void	setMappingReferencedLayerFields (const QStringList &fields)
	Sets the list of fields from the mappingTable() involved in the relationship.

void	setMappingReferencingLayerFields (const QStringList &fields)
	Sets the list of fields from the mappingTable() involved in the relationship.

void	setMappingTable (const QgsVectorLayerRef &table)
	Sets a weak reference to the mapping table, which forms the middle table in many-to-many relationships.

void	setMappingTable (const QString &sourceUri, const QString &provider)
	Sets the source for the mapping table, which forms the middle table in many-to-many relationships, by sourceUri and provider ID.

void	setReferencedLayer (const QString &sourceUri, const QString &provider)
	Sets the source for the referenced (or "parent" / "left") layer, by sourceUri and provider ID.

void	setReferencedLayerFields (const QStringList &fields)
	Sets the list of fields from the referencedLayer() involved in the relationship.

void	setReferencingLayer (const QString &sourceUri, const QString &provider)
	Sets the source for the referencing (or "child" / "right") layer, by sourceUri and provider ID.

void	setReferencingLayerFields (const QStringList &fields)
	Sets the list of fields from the referencingLayer() involved in the relationship.

void	setRelatedTableType (const QString &type)
	Sets the type string of the related table.

Qgis::RelationshipStrength	strength () const
	Returns the strength of the relation.

Static Public Member Functions
static QgsWeakRelation	readXml (const QgsVectorLayer *layer, WeakRelationType type, const QDomNode &node, const QgsPathResolver resolver)
	Returns a weak relation for the given layer.

static void	writeXml (const QgsVectorLayer *layer, WeakRelationType type, const QgsRelation &relation, QDomNode &node, QDomDocument &doc)
	Writes a weak relation infoto an XML structure.

Friends
class	TestQgsWeakRelation

Detailed Description

The QgsWeakRelation class represent a QgsRelation with possibly unresolved layers or unmatched fields.

This class is used to store relation information attached to a layer style, a method to attempt relation resolution is also implemented and can be used to create a QgsRelation after the dependent layers are loaded and available.

In contrast to QgsRelation, QgsWeakRelation can be used to encapsulate information about a relationship which does not currently exist in a QGIS project. E.g. it can be used to represent a relationship which exists in a database backend (but not within a QGIS project). Accordingly, some properties available in QgsWeakRelation are included for informational purposes only, and cannot be translated to QgsRelations or respected in QGIS relationships.

Since: QGIS 3.12

Definition at line 42 of file qgsweakrelation.h.

Member Enumeration Documentation

◆ WeakRelationType

enum QgsWeakRelation::WeakRelationType

Enum to distinguish if the layer is referenced or referencing.

Since: QGIS 3.16

Enumerator
Referencing	The layer is referencing (or the "child" / "right" layer in the relationship)
Referenced	The layer is referenced (or the "parent" / "left" left in the relationship)

Definition at line 50 of file qgsweakrelation.h.

Constructor & Destructor Documentation

◆ QgsWeakRelation() [1/2]

QgsWeakRelation::QgsWeakRelation ( )

default

Default constructor for an invalid relation.

◆ QgsWeakRelation() [2/2]

QgsWeakRelation::QgsWeakRelation	(	const QString &	relationId,
		const QString &	relationName,
		const Qgis::RelationshipStrength	strength,
		const QString &	referencingLayerId,
		const QString &	referencingLayerName,
		const QString &	referencingLayerSource,
		const QString &	referencingLayerProviderKey,
		const QString &	referencedLayerId,
		const QString &	referencedLayerName,
		const QString &	referencedLayerSource,
		const QString &	referencedLayerProviderKey
	)

Creates a QgsWeakRelation.

Since: QGIS 3.30

Definition at line 25 of file qgsweakrelation.cpp.

Member Function Documentation

◆ backwardPathLabel()

QString QgsWeakRelation::backwardPathLabel ( ) const

inline

Returns the label of the backward path for the relationship.

The forward and backward path labels are free-form, user-friendly strings which can be used to generate descriptions of the relationship between features from the right and left tables.

E.g. when the left table contains buildings and the right table contains furniture, the forward path label could be "contains" and the backward path label could be "is located within". A client could then generate a user friendly description string such as "fire hose 1234 is located within building 15a".

See also: setBackwardPathLabel(); forwardPathLabel()

Since: QGIS 3.28

Definition at line 370 of file qgsweakrelation.h.

◆ cardinality()

Qgis::RelationshipCardinality QgsWeakRelation::cardinality ( ) const

inline

Returns the relationship's cardinality.

See also: setCardinality()

Since: QGIS 3.28

Definition at line 324 of file qgsweakrelation.h.

◆ forwardPathLabel()

QString QgsWeakRelation::forwardPathLabel ( ) const

inline

Returns the label of the forward path for the relationship.

The forward and backward path labels are free-form, user-friendly strings which can be used to generate descriptions of the relationship between features from the right and left tables.

E.g. when the left table contains buildings and the right table contains furniture, the forward path label could be "contains" and the backward path label could be "is located within". A client could then generate a user friendly description string such as "fire hose 1234 is located within building 15a".

See also: setForwardPathLabel(); backwardPathLabel()

Since: QGIS 3.28

Definition at line 351 of file qgsweakrelation.h.

◆ id()

QString QgsWeakRelation::id ( ) const

inline

Returns the relationship's ID.

Since: QGIS 3.28

Definition at line 97 of file qgsweakrelation.h.

◆ mappingReferencedLayerFields()

QStringList QgsWeakRelation::mappingReferencedLayerFields ( ) const

inline

Returns the list of fields from the mappingTable() involved in the relationship.

These fields will be matched to the referencedLayerFields() in many-to-many joins.

Since: QGIS 3.28

Definition at line 302 of file qgsweakrelation.h.

◆ mappingReferencingLayerFields()

QStringList QgsWeakRelation::mappingReferencingLayerFields ( ) const

inline

Returns the list of fields from the mappingTable() involved in the relationship.

These fields will be matched to the referencingLayerFields() in many-to-many joins.

Since: QGIS 3.28

Definition at line 270 of file qgsweakrelation.h.

◆ mappingTable()

QgsVectorLayerRef QgsWeakRelation::mappingTable ( ) const

Returns a weak reference to the mapping table, which forms the middle table in many-to-many relationships.

Note: Not available in Python bindings.

Since: QGIS 3.28

Definition at line 190 of file qgsweakrelation.cpp.

◆ mappingTableName()

QString QgsWeakRelation::mappingTableName ( ) const

Returns the layer name of the mapping table, which forms the middle table in many-to-many relationships.

Note: the layer name refers to the layer name used in the datasource, not in any associated QgsVectorLayer.

Since: QGIS 3.28

Definition at line 210 of file qgsweakrelation.cpp.

◆ mappingTableProvider()

QString QgsWeakRelation::mappingTableProvider ( ) const

Returns the provider ID for the mapping table, which forms the middle table in many-to-many relationships.

See also: mappingTableSource(); setMappingTable()

Since: QGIS 3.28

Definition at line 205 of file qgsweakrelation.cpp.

◆ mappingTableSource()

QString QgsWeakRelation::mappingTableSource ( ) const

Returns the source URI for the mapping table, which forms the middle table in many-to-many relationships.

See also: mappingTableProvider(); setMappingTable()

Since: QGIS 3.28

Definition at line 200 of file qgsweakrelation.cpp.

◆ name()

QString QgsWeakRelation::name ( ) const

inline

Returns the relationship's name.

Since: QGIS 3.28

Definition at line 104 of file qgsweakrelation.h.

◆ readXml()

QgsWeakRelation QgsWeakRelation::readXml	(	const QgsVectorLayer *	layer,
		WeakRelationType	type,
		const QDomNode &	node,
		const QgsPathResolver	resolver
	)

static

Returns a weak relation for the given layer.

Parameters

layer	the layer of the weak relation
type	determines if the layer is referencing or referenced
node	the QDomNode
resolver	the path resolver

Since: QGIS 3.16

Definition at line 230 of file qgsweakrelation.cpp.

◆ referencedLayer()

QgsVectorLayerRef QgsWeakRelation::referencedLayer ( ) const

Returns a weak reference to the referenced (or "parent" / "left") layer.

Note: Not available in Python bindings.

Definition at line 160 of file qgsweakrelation.cpp.

◆ referencedLayerFields()

QStringList QgsWeakRelation::referencedLayerFields ( ) const

inline

Returns the list of fields from the referencedLayer() involved in the relationship.

Since: QGIS 3.28

Definition at line 286 of file qgsweakrelation.h.

◆ referencedLayerName()

QString QgsWeakRelation::referencedLayerName ( ) const

Returns the layer name of the referenced (or "parent" / "left") layer.

Note: the layer name refers to the layer name used in the datasource, not in any associated QgsVectorLayer.

Since: QGIS 3.28

Definition at line 175 of file qgsweakrelation.cpp.

◆ referencedLayerProvider()

QString QgsWeakRelation::referencedLayerProvider ( ) const

Returns the provider ID for the referenced (or "parent" / "left") layer.

See also: referencedLayerSource(); setReferencedLayer()

Since: QGIS 3.28

Definition at line 170 of file qgsweakrelation.cpp.

◆ referencedLayerSource()

QString QgsWeakRelation::referencedLayerSource ( ) const

Returns the source URI for the referenced (or "parent" / "left") layer.

See also: referencedLayerProvider(); setReferencedLayer()

Since: QGIS 3.28

Definition at line 165 of file qgsweakrelation.cpp.

◆ referencingLayer()

QgsVectorLayerRef QgsWeakRelation::referencingLayer ( ) const

Returns a weak reference to the referencing (or "child" / "right") layer.

Note: Not available in Python bindings.

Definition at line 130 of file qgsweakrelation.cpp.

◆ referencingLayerFields()

QStringList QgsWeakRelation::referencingLayerFields ( ) const

inline

Returns the list of fields from the referencingLayer() involved in the relationship.

Since: QGIS 3.28

Definition at line 254 of file qgsweakrelation.h.

◆ referencingLayerName()

QString QgsWeakRelation::referencingLayerName ( ) const

Returns the layer name of the referencing (or "child" / "right") layer.

Note: the layer name refers to the layer name used in the datasource, not in any associated QgsVectorLayer.

Since: QGIS 3.28

Definition at line 151 of file qgsweakrelation.cpp.

◆ referencingLayerProvider()

QString QgsWeakRelation::referencingLayerProvider ( ) const

Returns the provider ID for the referencing (or "child" / "right") layer.

See also: referencingLayerSource(); setReferencingLayer()

Since: QGIS 3.28

Definition at line 140 of file qgsweakrelation.cpp.

◆ referencingLayerSource()

QString QgsWeakRelation::referencingLayerSource ( ) const

Returns the source URI for the referencing (or "child" / "right") layer.

See also: referencingLayerProvider(); setReferencingLayer()

Since: QGIS 3.28

Definition at line 135 of file qgsweakrelation.cpp.

◆ relatedTableType()

QString QgsWeakRelation::relatedTableType ( ) const

inline

Returns the type string of the related table.

This a free-form string representing the type of related features, where the exact interpretation is format dependent. For instance, table types from GeoPackage relationships will directly reflect the categories from the GeoPackage related tables extension (i.e. "media", "simple attributes", "features", "attributes" and "tiles").

See also: setRelatedTableType()

Since: QGIS 3.28

Definition at line 421 of file qgsweakrelation.h.

◆ resolvedRelations()

QList< QgsRelation > QgsWeakRelation::resolvedRelations	(	const QgsProject *	project,
		QgsVectorLayerRef::MatchType	matchType = `QgsVectorLayerRef::MatchType::All`
	)		const

Resolves a weak relation in the given project returning a list of possibly invalid QgsRelations and without performing any kind of validity check.

Note: Client code should never assume that the returned relations are valid and the layer components are not NULL.

Definition at line 36 of file qgsweakrelation.cpp.

◆ setBackwardPathLabel()

void QgsWeakRelation::setBackwardPathLabel ( const QString & label )

inline

Sets the label of the backward path for the relationship.

The forward and backward path labels are free-form, user-friendly strings which can be used to generate descriptions of the relationship between features from the right and left tables.

E.g. when the left table contains buildings and the right table contains furniture, the forward path label could be "contains" and the backward path label could be "is located within". A client could then generate a user friendly description string such as "fire hose 1234 is located within building 15a".

See also: backwardPathLabel(); setForwardPathLabel()

Since: QGIS 3.28

Definition at line 408 of file qgsweakrelation.h.

◆ setCardinality()

void QgsWeakRelation::setCardinality ( Qgis::RelationshipCardinality cardinality )

inline

Sets the relationship's cardinality.

See also: cardinality()

Since: QGIS 3.28

Definition at line 332 of file qgsweakrelation.h.

◆ setForwardPathLabel()

void QgsWeakRelation::setForwardPathLabel ( const QString & label )

inline

Sets the label of the forward path for the relationship.

The forward and backward path labels are free-form, user-friendly strings which can be used to generate descriptions of the relationship between features from the right and left tables.

E.g. when the left table contains buildings and the right table contains furniture, the forward path label could be "contains" and the backward path label could be "is located within". A client could then generate a user friendly description string such as "fire hose 1234 is located within building 15a".

See also: forwardPathLabel(); setBackwardPathLabel()

Since: QGIS 3.28

Definition at line 389 of file qgsweakrelation.h.

◆ setMappingReferencedLayerFields()

void QgsWeakRelation::setMappingReferencedLayerFields ( const QStringList & fields )

inline

Sets the list of fields from the mappingTable() involved in the relationship.

These fields will be matched to the referencedLayerFields() in many-to-many joins.

Since: QGIS 3.28

Definition at line 311 of file qgsweakrelation.h.

◆ setMappingReferencingLayerFields()

void QgsWeakRelation::setMappingReferencingLayerFields ( const QStringList & fields )

inline

Sets the list of fields from the mappingTable() involved in the relationship.

These fields will be matched to the referencingLayerFields() in many-to-many joins.

Since: QGIS 3.28

Definition at line 279 of file qgsweakrelation.h.

◆ setMappingTable() [1/2]

void QgsWeakRelation::setMappingTable ( const QgsVectorLayerRef & table )

Sets a weak reference to the mapping table, which forms the middle table in many-to-many relationships.

Note: Not available in Python bindings.

Since: QGIS 3.28

Definition at line 195 of file qgsweakrelation.cpp.

◆ setMappingTable() [2/2]

void QgsWeakRelation::setMappingTable	(	const QString &	sourceUri,
		const QString &	provider
	)

Sets the source for the mapping table, which forms the middle table in many-to-many relationships, by sourceUri and provider ID.

See also: mappingTableSource(); mappingTableProvider()

Since: QGIS 3.36

Definition at line 219 of file qgsweakrelation.cpp.

◆ setReferencedLayer()

void QgsWeakRelation::setReferencedLayer	(	const QString &	sourceUri,
		const QString &	provider
	)

Sets the source for the referenced (or "parent" / "left") layer, by sourceUri and provider ID.

See also: referencedLayerSource(); referencedLayerProvider()

Since: QGIS 3.36

Definition at line 184 of file qgsweakrelation.cpp.

◆ setReferencedLayerFields()

void QgsWeakRelation::setReferencedLayerFields ( const QStringList & fields )

inline

Sets the list of fields from the referencedLayer() involved in the relationship.

Since: QGIS 3.28

Definition at line 293 of file qgsweakrelation.h.

◆ setReferencingLayer()

void QgsWeakRelation::setReferencingLayer	(	const QString &	sourceUri,
		const QString &	provider
	)

Sets the source for the referencing (or "child" / "right") layer, by sourceUri and provider ID.

See also: referencingLayerSource(); referencingLayerProvider()

Since: QGIS 3.36

Definition at line 145 of file qgsweakrelation.cpp.

◆ setReferencingLayerFields()

void QgsWeakRelation::setReferencingLayerFields ( const QStringList & fields )

inline

Sets the list of fields from the referencingLayer() involved in the relationship.

Since: QGIS 3.28

Definition at line 261 of file qgsweakrelation.h.

◆ setRelatedTableType()

void QgsWeakRelation::setRelatedTableType ( const QString & type )

inline

Sets the type string of the related table.

This a free-form string representing the type of related features, where the exact interpretation is format dependent. For instance, table types from GeoPackage relationships will directly reflect the categories from the GeoPackage related tables extension (i.e. "media", "simple attributes", "features", "attributes" and "tiles").

See also: relatedTableType()

Since: QGIS 3.28

Definition at line 434 of file qgsweakrelation.h.

◆ strength()

Qgis::RelationshipStrength QgsWeakRelation::strength ( ) const

Returns the strength of the relation.

Definition at line 225 of file qgsweakrelation.cpp.

◆ writeXml()

void QgsWeakRelation::writeXml	(	const QgsVectorLayer *	layer,
		WeakRelationType	type,
		const QgsRelation &	relation,
		QDomNode &	node,
		QDomDocument &	doc
	)

static

Writes a weak relation infoto an XML structure.

Used for saving .qgs projects

Parameters

layer	the layer which we save the weak relation for
type	determines if the layer is referencing or referenced
relation	the relation to save as a weak relation
node	The parent node in which the relation will be created
doc	The document in which the relation will be saved

Since: QGIS 3.16

Definition at line 298 of file qgsweakrelation.cpp.

Friends And Related Symbol Documentation

◆ TestQgsWeakRelation

friend class TestQgsWeakRelation

friend

Definition at line 501 of file qgsweakrelation.h.

The documentation for this class was generated from the following files:

/build/qgis-3.41.0+git20241214+cea29feecf2+99sid/src/core/qgsweakrelation.h
/build/qgis-3.41.0+git20241214+cea29feecf2+99sid/src/core/qgsweakrelation.cpp

Public Types

Public Member Functions

Static Public Member Functions

Friends

Detailed Description

Member Enumeration Documentation

◆ WeakRelationType

Constructor & Destructor Documentation

◆ QgsWeakRelation() [1/2]

◆ QgsWeakRelation() [2/2]

Member Function Documentation

◆ backwardPathLabel()

◆ cardinality()

◆ forwardPathLabel()

◆ id()

◆ mappingReferencedLayerFields()

◆ mappingReferencingLayerFields()

◆ mappingTable()

◆ mappingTableName()

◆ mappingTableProvider()

◆ mappingTableSource()

◆ name()

◆ readXml()

◆ referencedLayer()

◆ referencedLayerFields()

◆ referencedLayerName()

◆ referencedLayerProvider()

◆ referencedLayerSource()

◆ referencingLayer()

◆ referencingLayerFields()

◆ referencingLayerName()

◆ referencingLayerProvider()

◆ referencingLayerSource()

◆ relatedTableType()

◆ resolvedRelations()

◆ setBackwardPathLabel()

◆ setCardinality()

◆ setForwardPathLabel()

◆ setMappingReferencedLayerFields()

◆ setMappingReferencingLayerFields()

◆ setMappingTable() [1/2]

◆ setMappingTable() [2/2]

◆ setReferencedLayer()

◆ setReferencedLayerFields()

◆ setReferencingLayer()

◆ setReferencingLayerFields()

◆ setRelatedTableType()

◆ strength()

◆ writeXml()

Friends And Related Symbol Documentation

◆ TestQgsWeakRelation