#include <qgsrelation.h>

Classes
class	FieldPair
	Defines a relation between matching fields of the two involved tables of a relation. More...

Public Types
enum	RelationStrength { Association , Composition }
	enum for the relation strength Association, Composition More...

enum	RelationType { Normal , Generated }
	Enum holding the relations type. More...

Public Member Functions
	QgsRelation ()
	Default constructor. More...

	QgsRelation (const QgsRelation &other)
	Copies a relation. More...

	QgsRelation (const QgsRelationContext &context)
	Constructor with context. More...

	~QgsRelation ()

void	addFieldPair (const FieldPair &fieldPair)
	Add a field pair which is part of this relation The first element of each pair are the field names of the foreign key. More...

void	addFieldPair (const QString &referencingField, const QString &referencedField)
	Add a field pair which is part of this relation The first element of each pair are the field names of the foreign key. More...

QList< QgsRelation::FieldPair >	fieldPairs () const
	Returns the field pairs which form this relation The first element of each pair are the field names of the foreign key. More...

void	generateId ()
	Generate a (project-wide) unique id for this relation. More...

QgsFeature	getReferencedFeature (const QgsFeature &feature) const
	Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature. More...

QgsFeatureRequest	getReferencedFeatureRequest (const QgsAttributes &attributes) const
	Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature. More...

QgsFeatureRequest	getReferencedFeatureRequest (const QgsFeature &feature) const
	Creates a request to return the feature on the referenced (parent) layer which is referenced by the provided feature. More...

QgsFeatureIterator	getRelatedFeatures (const QgsFeature &feature) const
	Creates an iterator which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. More...

QString	getRelatedFeaturesFilter (const QgsFeature &feature) const
	Returns a filter expression which returns all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. More...

QgsFeatureRequest	getRelatedFeaturesRequest (const QgsFeature &feature) const
	Creates a request to return all the features on the referencing (child) layer which have a foreign key pointing to the provided feature. More...

bool	hasEqualDefinition (const QgsRelation &other) const
	Compares the two QgsRelation, ignoring the name and the ID. More...

QString	id () const
	A (project-wide) unique id for this relation. More...

bool	isValid () const
	Returns the validity of this relation. More...

QString	name () const
	Returns a human readable name for this relation. More...

QgsRelation &	operator= (const QgsRelation &other)
	Copies a relation. More...

QgsPolymorphicRelation	polymorphicRelation () const
	Returns the parent polymorphic relation. More...

QString	polymorphicRelationId () const
	Returns the parent polymorphic relation id. More...

QgsAttributeList	referencedFields () const
	Returns a list of attributes used to form the referenced fields (most likely primary key) on the referenced (parent) layer. More...

QgsVectorLayer *	referencedLayer () const
	Access the referenced (parent) layer. More...

QString	referencedLayerId () const
	Access the referenced (parent) layer's id. More...

QgsAttributeList	referencingFields () const
	Returns a list of attributes used to form the referencing fields (foreign key) on the referencing (child) layer. More...

QgsVectorLayer *	referencingLayer () const
	Access the referencing (child) layer This is the layer which has the field(s) which point to another layer. More...

QString	referencingLayerId () const
	Access the referencing (child) layer's id This is the layer which has the field(s) which point to another layer. More...

Q_INVOKABLE QString	resolveReferencedField (const QString &referencingField) const
	Gets the referenced field counterpart given a referencing field. More...

Q_INVOKABLE QString	resolveReferencingField (const QString &referencedField) const
	Gets the referencing field counterpart given a referenced field. More...

void	setId (const QString &id)
	Set an id for this relation. More...

void	setName (const QString &name)
	Set a name for this relation. More...

void	setPolymorphicRelationId (const QString &polymorphicRelationId)
	Sets the parent polymorphic relation id. More...

void	setReferencedLayer (const QString &id)
	Set the referenced (parent) layer id. More...

void	setReferencingLayer (const QString &id)
	Set the referencing (child) layer id. More...

void	setStrength (RelationStrength strength)
	Set a strength for this relation. More...

RelationStrength	strength () const
	Returns the relation strength as a string. More...

RelationType	type () const
	Returns the type of the relation. More...

void	updateRelationStatus ()
	Updates the validity status of this relation. More...

void	writeXml (QDomNode &node, QDomDocument &doc) const
	Writes a relation to an XML structure. More...

Static Public Member Functions
static QgsRelation	createFromXml (const QDomNode &node, QgsReadWriteContext &context, const QgsRelationContext &relationContext=QgsRelationContext())
	Creates a relation from an XML structure. More...

Properties
Q_GADGET QString	id

bool	isValid

QString	name

QgsPolymorphicRelation	polymorphicRelation

QString	polymorphicRelationId

QgsVectorLayer *	referencedLayer

QgsVectorLayer *	referencingLayer

Detailed Description

Definition at line 42 of file qgsrelation.h.

Member Enumeration Documentation

◆ RelationStrength

enum QgsRelation::RelationStrength

enum for the relation strength Association, Composition

Enumerator
Association	Loose relation, related elements are not part of the parent and a parent copy will not copy any children.
Composition	Fix relation, related elements are part of the parent and a parent copy will copy any children or delete of parent will delete children.

Definition at line 70 of file qgsrelation.h.

◆ RelationType

enum QgsRelation::RelationType

Enum holding the relations type.

Enumerator
Normal	A normal relation.
Generated	A generated relation is a child of a polymorphic relation.

Definition at line 59 of file qgsrelation.h.

Constructor & Destructor Documentation

◆ QgsRelation() [1/3]

QgsRelation::QgsRelation ( )

Default constructor.

Creates an invalid relation.

Definition at line 27 of file qgsrelation.cpp.

◆ ~QgsRelation()

QgsRelation::~QgsRelation ( )

default

◆ QgsRelation() [2/3]

QgsRelation::QgsRelation ( const QgsRelationContext & context )

Constructor with context.

Creates an invalid relation.

Definition at line 32 of file qgsrelation.cpp.

◆ QgsRelation() [3/3]

QgsRelation::QgsRelation ( const QgsRelation & other )

Copies a relation.

This makes a shallow copy, relations are implicitly shared and only duplicated when the copy is changed.

Definition at line 40 of file qgsrelation.cpp.

Member Function Documentation

◆ addFieldPair() [1/2]

void QgsRelation::addFieldPair ( const FieldPair & fieldPair )

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

fieldPair A pair of two strings

Note: not available in Python bindings

Definition at line 181 of file qgsrelation.cpp.

◆ addFieldPair() [2/2]

void QgsRelation::addFieldPair	(	const QString &	referencingField,
		const QString &	referencedField
	)

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	The field name on the referencing (child) layer (FK)
referencedField	The field name on the referenced (parent) layer (PK)

Definition at line 174 of file qgsrelation.cpp.

◆ createFromXml()

QgsRelation QgsRelation::createFromXml	(	const QDomNode &	node,
		QgsReadWriteContext &	context,
		const QgsRelationContext &	relationContext = `QgsRelationContext()`
	)

static

Creates a relation from an XML structure.

Used for reading .qgs projects.

Parameters

node	The dom node containing the relation information
context	to pass project translator
relationContext	a relation context

Returns: A relation

Definition at line 53 of file qgsrelation.cpp.

◆ fieldPairs()

QList< QgsRelation::FieldPair > QgsRelation::fieldPairs ( ) const

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

Definition at line 312 of file qgsrelation.cpp.

◆ generateId()

void QgsRelation::generateId ( )

Generate a (project-wide) unique id for this relation.

Since: QGIS 3.0

Definition at line 278 of file qgsrelation.cpp.

◆ getReferencedFeature()

QgsFeature QgsRelation::getReferencedFeature ( const QgsFeature & feature ) const

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

Definition at line 254 of file qgsrelation.cpp.

◆ getReferencedFeatureRequest() [1/2]

QgsFeatureRequest QgsRelation::getReferencedFeatureRequest ( const QgsAttributes & attributes ) const

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

Definition at line 230 of file qgsrelation.cpp.

◆ getReferencedFeatureRequest() [2/2]

QgsFeatureRequest QgsRelation::getReferencedFeatureRequest ( const QgsFeature & feature ) const

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

Definition at line 249 of file qgsrelation.cpp.

◆ getRelatedFeatures()

QgsFeatureIterator QgsRelation::getRelatedFeatures ( const QgsFeature & feature ) const

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: getRelatedFeaturesRequest(); getRelatedFeaturesFilter()

Definition at line 188 of file qgsrelation.cpp.

◆ getRelatedFeaturesFilter()

QString QgsRelation::getRelatedFeaturesFilter ( const QgsFeature & feature ) const

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

See also: getRelatedFeatures(); getRelatedFeaturesRequest()

Since: QGIS 2.16

Definition at line 203 of file qgsrelation.cpp.

◆ getRelatedFeaturesRequest()

QgsFeatureRequest QgsRelation::getRelatedFeaturesRequest ( const QgsFeature & feature ) const

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: getRelatedFeatures(); getRelatedFeaturesFilter()

Definition at line 193 of file qgsrelation.cpp.

◆ hasEqualDefinition()

bool QgsRelation::hasEqualDefinition ( const QgsRelation & other ) const

Compares the two QgsRelation, ignoring the name and the ID.

Parameters

other The other relation

Returns: true if they are similar

Since: QGIS 3.0

Definition at line 345 of file qgsrelation.cpp.

◆ id()

QString QgsRelation::id ( ) const

A (project-wide) unique id for this relation.

Returns: The id

Definition at line 273 of file qgsrelation.cpp.

◆ isValid()

bool QgsRelation::isValid ( ) const

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.

Returns: true if the relation is valid

Definition at line 340 of file qgsrelation.cpp.

◆ name()

QString QgsRelation::name ( ) const

Returns a human readable name for this relation.

Mostly used as title for the children.

See also: id()

Returns: A name

Definition at line 263 of file qgsrelation.cpp.

◆ operator=()

QgsRelation & QgsRelation::operator= ( const QgsRelation & other )

Copies a relation.

This makes a shallow copy, relations are implicitly shared and only duplicated when the copy is changed.

Definition at line 46 of file qgsrelation.cpp.

◆ polymorphicRelation()

QgsPolymorphicRelation QgsRelation::polymorphicRelation ( ) const

Returns the parent polymorphic relation.

If the relation is a normal relation, an invalid polymorphic relation is returned.

Since: QGIS 3.18

Definition at line 435 of file qgsrelation.cpp.

◆ polymorphicRelationId()

QString QgsRelation::polymorphicRelationId ( ) const

Returns the parent polymorphic relation id.

If the relation is a normal relation, a null string is returned.

Since: QGIS 3.18

Definition at line 430 of file qgsrelation.cpp.

◆ referencedFields()

QgsAttributeList QgsRelation::referencedFields ( ) const

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

Definition at line 317 of file qgsrelation.cpp.

◆ referencedLayer()

QgsVectorLayer * QgsRelation::referencedLayer ( ) const

Access the referenced (parent) layer.

Returns: referenced layer

Definition at line 307 of file qgsrelation.cpp.

◆ referencedLayerId()

QString QgsRelation::referencedLayerId ( ) const

Access the referenced (parent) layer's id.

Returns: The id of the referenced layer

Definition at line 302 of file qgsrelation.cpp.

◆ referencingFields()

QgsAttributeList QgsRelation::referencingFields ( ) const

Returns a list of attributes used to form the referencing fields (foreign key) on the referencing (child) layer.

Returns: A list of attributes

Definition at line 328 of file qgsrelation.cpp.

◆ referencingLayer()

QgsVectorLayer * QgsRelation::referencingLayer ( ) const

Access the referencing (child) layer This is the layer which has the field(s) which point to another layer.

Returns: The referencing layer

Definition at line 297 of file qgsrelation.cpp.

◆ referencingLayerId()

QString QgsRelation::referencingLayerId ( ) const

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

Definition at line 292 of file qgsrelation.cpp.

◆ resolveReferencedField()

QString QgsRelation::resolveReferencedField ( const QString & referencingField ) const

Gets the referenced field counterpart given a referencing field.

Since: QGIS 3.0

Definition at line 350 of file qgsrelation.cpp.

◆ resolveReferencingField()

QString QgsRelation::resolveReferencingField ( const QString & referencedField ) const

Gets the referencing field counterpart given a referenced field.

Since: QGIS 3.0

Definition at line 360 of file qgsrelation.cpp.

◆ setId()

void QgsRelation::setId ( const QString & id )

Set an id for this relation.

Definition at line 137 of file qgsrelation.cpp.

◆ setName()

void QgsRelation::setName ( const QString & name )

Set a name for this relation.

Definition at line 145 of file qgsrelation.cpp.

◆ setPolymorphicRelationId()

void QgsRelation::setPolymorphicRelationId ( const QString & polymorphicRelationId )

Sets the parent polymorphic relation id.

Since: QGIS 3.18

Definition at line 424 of file qgsrelation.cpp.

◆ setReferencedLayer()

void QgsRelation::setReferencedLayer ( const QString & id )

Set the referenced (parent) layer id.

This layer will be searched in the registry.

Definition at line 166 of file qgsrelation.cpp.

◆ setReferencingLayer()

void QgsRelation::setReferencingLayer ( const QString & id )

Set the referencing (child) layer id.

This layer will be searched in the registry.

Definition at line 158 of file qgsrelation.cpp.

◆ setStrength()

void QgsRelation::setStrength ( RelationStrength strength )

Set a strength for this relation.

Since: QGIS 3.0

Definition at line 152 of file qgsrelation.cpp.

◆ strength()

QgsRelation::RelationStrength QgsRelation::strength ( ) const

Returns the relation strength as a string.

Returns: strength

Since: QGIS 3.0

Definition at line 268 of file qgsrelation.cpp.

◆ type()

QgsRelation::RelationType QgsRelation::type ( ) const

Returns the type of the relation.

Since: QGIS 3.18

Definition at line 443 of file qgsrelation.cpp.

◆ updateRelationStatus()

void QgsRelation::updateRelationStatus ( )

Updates the validity status of this relation.

Will be called internally whenever a member is changed.

Since: QGIS 3.6

Definition at line 370 of file qgsrelation.cpp.

◆ writeXml()

void QgsRelation::writeXml	(	QDomNode &	node,
		QDomDocument &	doc
	)		const

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

Definition at line 117 of file qgsrelation.cpp.

Property Documentation

◆ id

Q_GADGET QString QgsRelation::id

readwrite

Definition at line 44 of file qgsrelation.h.

◆ isValid

bool QgsRelation::isValid

read

Definition at line 44 of file qgsrelation.h.

◆ name

QString QgsRelation::name

readwrite

Definition at line 44 of file qgsrelation.h.

◆ polymorphicRelation

QgsPolymorphicRelation QgsRelation::polymorphicRelation

read

Definition at line 44 of file qgsrelation.h.

◆ polymorphicRelationId

QString QgsRelation::polymorphicRelationId

readwrite

Definition at line 44 of file qgsrelation.h.

◆ referencedLayer

QgsVectorLayer * QgsRelation::referencedLayer

read

Definition at line 44 of file qgsrelation.h.

◆ referencingLayer

QgsVectorLayer * QgsRelation::referencingLayer

read

Definition at line 44 of file qgsrelation.h.

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

/build/qgis-3.20.0+99unstable/src/core/qgsrelation.h
/build/qgis-3.20.0+99unstable/src/core/qgsrelation.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Properties

Detailed Description

Member Enumeration Documentation

◆ RelationStrength

◆ RelationType

Constructor & Destructor Documentation

◆ QgsRelation() [1/3]

◆ ~QgsRelation()

◆ QgsRelation() [2/3]

◆ QgsRelation() [3/3]

Member Function Documentation

◆ addFieldPair() [1/2]

◆ addFieldPair() [2/2]

◆ createFromXml()

◆ fieldPairs()

◆ generateId()

◆ getReferencedFeature()

◆ getReferencedFeatureRequest() [1/2]

◆ getReferencedFeatureRequest() [2/2]

◆ getRelatedFeatures()

◆ getRelatedFeaturesFilter()

◆ getRelatedFeaturesRequest()

◆ hasEqualDefinition()

◆ id()

◆ isValid()

◆ name()

◆ operator=()

◆ polymorphicRelation()

◆ polymorphicRelationId()

◆ referencedFields()

◆ referencedLayer()

◆ referencedLayerId()

◆ referencingFields()

◆ referencingLayer()

◆ referencingLayerId()

◆ resolveReferencedField()

◆ resolveReferencingField()

◆ setId()

◆ setName()

◆ setPolymorphicRelationId()

◆ setReferencedLayer()

◆ setReferencingLayer()

◆ setStrength()

◆ strength()

◆ type()

◆ updateRelationStatus()

◆ writeXml()

Property Documentation

◆ id

◆ isValid

◆ name

◆ polymorphicRelation

◆ polymorphicRelationId

◆ referencedLayer

◆ referencingLayer