A polymorphic relation consists of the same properties like a normal relation except for the referenced layer which is calculated based on one or several fields of the referencing layer. More...

#include <qgspolymorphicrelation.h>

Public Member Functions
	QgsPolymorphicRelation ()
	Default constructor.

	QgsPolymorphicRelation (const QgsPolymorphicRelation &other)
	Copies a relation.

	QgsPolymorphicRelation (const QgsRelationContext &context)
	Constructor with context.

	~QgsPolymorphicRelation ()

void	addFieldPair (const QgsRelation::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.

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.

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.

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

QList< QgsRelation >	generateRelations () const
	Returns a list of generated relations, based on the currently set referencedLayerIds()

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

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

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

QString	layerRepresentation (const QgsVectorLayer *layer) const
	Returns layer representation as evaluated string.

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

QgsPolymorphicRelation &	operator= (const QgsPolymorphicRelation &other)
	Copies a relation.

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

QString	referencedLayerExpression () const
	Returns the expression to identify the parent layer.

QString	referencedLayerField () const
	Returns the field in the referencing layer where the referenced layer identifier is stored.

QStringList	referencedLayerIds () const
	Returns a list of layer ids to be used as potential referenced layers.

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

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

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

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

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

void	setReferencedLayerExpression (const QString &expression)
	Sets the expression to identify the parent layer.

void	setReferencedLayerField (const QString &referencedLayerField)
	Sets the field in the referencing layer where the referenced layer identifier is stored.

void	setReferencedLayerIds (const QStringList &childRelationIds)
	Sets a list of layer ids to be used as potential referenced layers.

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

void	setRelationStrength (Qgis::RelationshipStrength relationStrength)
	Sets the relation strength for all the generated normal relations.

Qgis::RelationshipStrength	strength () const
	Returns the relation strength for all the generated normal relations.

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

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

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

Properties
QString	id

bool	isValid

QString	name

QString	referencedLayerExpression

QString	referencedLayerField

QgsVectorLayer *	referencingLayer

Friends
class	QgsRelationManager

Detailed Description

A polymorphic relation consists of the same properties like a normal relation except for the referenced layer which is calculated based on one or several fields of the referencing layer.

In its most simple form, the referencing layer will just insert the layer name of the referenced layer into this field. To be more precise, a polymorphic relation is a set of normal relations having the same referencing layer but having the referenced layer dynamically defined. The polymorphic setting of the layer is solved by using an expression which has to match some properties of the the referenced layer like the table name, schema, uri, layer id, ...

Since: QGIS 3.18

Definition at line 49 of file qgspolymorphicrelation.h.

Constructor & Destructor Documentation

◆ QgsPolymorphicRelation() [1/3]

QgsPolymorphicRelation::QgsPolymorphicRelation ( )

Default constructor.

Creates an invalid relation.

Definition at line 25 of file qgspolymorphicrelation.cpp.

◆ ~QgsPolymorphicRelation()

QgsPolymorphicRelation::~QgsPolymorphicRelation ( )

default

◆ QgsPolymorphicRelation() [2/3]

QgsPolymorphicRelation::QgsPolymorphicRelation ( const QgsRelationContext & context )

Constructor with context.

Creates an invalid relation.

Definition at line 30 of file qgspolymorphicrelation.cpp.

◆ QgsPolymorphicRelation() [3/3]

QgsPolymorphicRelation::QgsPolymorphicRelation ( const QgsPolymorphicRelation & other )

Copies a relation.

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

Definition at line 38 of file qgspolymorphicrelation.cpp.

Member Function Documentation

◆ addFieldPair() [1/2]

void QgsPolymorphicRelation::addFieldPair ( const QgsRelation::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 150 of file qgspolymorphicrelation.cpp.

◆ addFieldPair() [2/2]

void QgsPolymorphicRelation::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 143 of file qgspolymorphicrelation.cpp.

◆ createFromXml()

QgsPolymorphicRelation QgsPolymorphicRelation::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 51 of file qgspolymorphicrelation.cpp.

◆ fieldPairs()

QList< QgsRelation::FieldPair > QgsPolymorphicRelation::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 182 of file qgspolymorphicrelation.cpp.

◆ generateId()

void QgsPolymorphicRelation::generateId ( )

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

Definition at line 162 of file qgspolymorphicrelation.cpp.

◆ generateRelations()

QList< QgsRelation > QgsPolymorphicRelation::generateRelations ( ) const

Returns a list of generated relations, based on the currently set referencedLayerIds()

Definition at line 377 of file qgspolymorphicrelation.cpp.

◆ hasEqualDefinition()

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

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

Parameters

other The other relation

Returns: true if they are similar

Definition at line 224 of file qgspolymorphicrelation.cpp.

◆ id()

QString QgsPolymorphicRelation::id ( ) const

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

Returns: The id

Definition at line 157 of file qgspolymorphicrelation.cpp.

◆ isValid()

bool QgsPolymorphicRelation::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 219 of file qgspolymorphicrelation.cpp.

◆ layerRepresentation()

QString QgsPolymorphicRelation::layerRepresentation ( const QgsVectorLayer * layer ) const

Returns layer representation as evaluated string.

Definition at line 429 of file qgspolymorphicrelation.cpp.

◆ name()

QString QgsPolymorphicRelation::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 321 of file qgspolymorphicrelation.cpp.

◆ operator=()

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

Copies a relation.

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

Definition at line 44 of file qgspolymorphicrelation.cpp.

◆ referencedFields()

QgsAttributeList QgsPolymorphicRelation::referencedFields ( const QString & layerId ) 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 187 of file qgspolymorphicrelation.cpp.

◆ referencedLayerExpression()

QString QgsPolymorphicRelation::referencedLayerExpression ( ) const

Returns the expression to identify the parent layer.

Definition at line 348 of file qgspolymorphicrelation.cpp.

◆ referencedLayerField()

QString QgsPolymorphicRelation::referencedLayerField ( ) const

Returns the field in the referencing layer where the referenced layer identifier is stored.

Definition at line 336 of file qgspolymorphicrelation.cpp.

◆ referencedLayerIds()

QStringList QgsPolymorphicRelation::referencedLayerIds ( ) const

Returns a list of layer ids to be used as potential referenced layers.

Definition at line 360 of file qgspolymorphicrelation.cpp.

◆ referencingFields()

QgsAttributeList QgsPolymorphicRelation::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 207 of file qgspolymorphicrelation.cpp.

◆ referencingLayer()

QgsVectorLayer * QgsPolymorphicRelation::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 177 of file qgspolymorphicrelation.cpp.

◆ referencingLayerId()

QString QgsPolymorphicRelation::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 172 of file qgspolymorphicrelation.cpp.

◆ setId()

void QgsPolymorphicRelation::setId ( const QString & id )

Set an id for this relation.

Definition at line 124 of file qgspolymorphicrelation.cpp.

◆ setName()

void QgsPolymorphicRelation::setName ( const QString & name )

Set a name for this relation.

Definition at line 311 of file qgspolymorphicrelation.cpp.

◆ setReferencedLayerExpression()

void QgsPolymorphicRelation::setReferencedLayerExpression ( const QString & expression )

Sets the expression to identify the parent layer.

Definition at line 341 of file qgspolymorphicrelation.cpp.

◆ setReferencedLayerField()

void QgsPolymorphicRelation::setReferencedLayerField ( const QString & referencedLayerField )

Sets the field in the referencing layer where the referenced layer identifier is stored.

Definition at line 329 of file qgspolymorphicrelation.cpp.

◆ setReferencedLayerIds()

void QgsPolymorphicRelation::setReferencedLayerIds ( const QStringList & childRelationIds )

Sets a list of layer ids to be used as potential referenced layers.

Definition at line 353 of file qgspolymorphicrelation.cpp.

◆ setReferencingLayer()

void QgsPolymorphicRelation::setReferencingLayer ( const QString & id )

Set the referencing (child) layer id.

This layer will be searched in the registry.

Definition at line 135 of file qgspolymorphicrelation.cpp.

◆ setRelationStrength()

void QgsPolymorphicRelation::setRelationStrength ( Qgis::RelationshipStrength relationStrength )

Sets the relation strength for all the generated normal relations.

Definition at line 370 of file qgspolymorphicrelation.cpp.

◆ strength()

Qgis::RelationshipStrength QgsPolymorphicRelation::strength ( ) const

Returns the relation strength for all the generated normal relations.

Definition at line 365 of file qgspolymorphicrelation.cpp.

◆ updateRelationStatus()

void QgsPolymorphicRelation::updateRelationStatus ( )

Updates the validity status of this relation.

Will be called internally whenever a member is changed.

Definition at line 232 of file qgspolymorphicrelation.cpp.

◆ writeXml()

void QgsPolymorphicRelation::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 98 of file qgspolymorphicrelation.cpp.

Friends And Related Symbol Documentation

◆ QgsRelationManager

friend class QgsRelationManager

friend

Definition at line 288 of file qgspolymorphicrelation.h.

Property Documentation

◆ id

QString QgsPolymorphicRelation::id

readwrite

Definition at line 53 of file qgspolymorphicrelation.h.

◆ isValid

bool QgsPolymorphicRelation::isValid

read

Definition at line 58 of file qgspolymorphicrelation.h.

◆ name

QString QgsPolymorphicRelation::name

readwrite

Definition at line 57 of file qgspolymorphicrelation.h.

◆ referencedLayerExpression

QString QgsPolymorphicRelation::referencedLayerExpression

read

Definition at line 56 of file qgspolymorphicrelation.h.

◆ referencedLayerField

QString QgsPolymorphicRelation::referencedLayerField

read

Definition at line 55 of file qgspolymorphicrelation.h.

◆ referencingLayer

QgsVectorLayer * QgsPolymorphicRelation::referencingLayer

read

Definition at line 54 of file qgspolymorphicrelation.h.

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

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

Public Member Functions

Static Public Member Functions

Properties

Friends

Detailed Description

Constructor & Destructor Documentation

◆ QgsPolymorphicRelation() [1/3]

◆ ~QgsPolymorphicRelation()

◆ QgsPolymorphicRelation() [2/3]

◆ QgsPolymorphicRelation() [3/3]

Member Function Documentation

◆ addFieldPair() [1/2]

◆ addFieldPair() [2/2]

◆ createFromXml()

◆ fieldPairs()

◆ generateId()

◆ generateRelations()

◆ hasEqualDefinition()

◆ id()

◆ isValid()

◆ layerRepresentation()

◆ name()

◆ operator=()

◆ referencedFields()

◆ referencedLayerExpression()

◆ referencedLayerField()

◆ referencedLayerIds()

◆ referencingFields()

◆ referencingLayer()

◆ referencingLayerId()

◆ setId()

◆ setName()

◆ setReferencedLayerExpression()

◆ setReferencedLayerField()

◆ setReferencedLayerIds()

◆ setReferencingLayer()

◆ setRelationStrength()

◆ strength()

◆ updateRelationStatus()

◆ writeXml()

Friends And Related Symbol Documentation

◆ QgsRelationManager

Property Documentation

◆ id

◆ isValid

◆ name

◆ referencedLayerExpression

◆ referencedLayerField

◆ referencingLayer