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287 lines
9.1 KiB
C++
287 lines
9.1 KiB
C++
/***************************************************************************
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qgsrelation.h
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--------------------------------------
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Date : 29.4.2013
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Copyright : (C) 2013 Matthias Kuhn
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Email : matthias at opengis dot ch
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************/
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#ifndef QGSRELATION_H
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#define QGSRELATION_H
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#include <QList>
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#include <QDomNode>
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#include <QPair>
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#include "qgsfield.h"
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#include "qgsfeatureiterator.h"
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class QgsVectorLayer;
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class CORE_EXPORT QgsRelation
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{
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public:
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/**
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* Defines a relation between matching fields of the two involved tables of a relation.
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* Often, a relation is only defined by just one FieldPair with the name of the foreign key
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* column of the referencing (child) table as first element and the name of the primary key column
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* of the referenced (parent) table as the second element.
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* @note not available in Python bindings
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*/
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class FieldPair : public QPair< QString, QString >
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{
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public:
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//! Default constructor: NULL strings
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FieldPair()
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: QPair< QString, QString >() {}
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//! Constructor which takes two fields
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FieldPair( const QString& referencingField, const QString& referencedField )
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: QPair< QString, QString >( referencingField, referencedField ) {}
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//! Get the name of the referencing (child) field
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QString referencingField() const { return first; }
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//! Get the name of the referenced (parent) field
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QString referencedField() const { return second; }
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};
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/**
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* Default constructor. Creates an invalid relation.
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*/
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QgsRelation();
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/**
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* Creates a relation from an XML structure. Used for reading .qgs projects.
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*
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* @param node The dom node containing the relation information
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*
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* @return A relation
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*/
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static QgsRelation createFromXML( const QDomNode& node );
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/**
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* Writes a relation to an XML structure. Used for saving .qgs projects
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*
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* @param node The parent node in which the relation will be created
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* @param doc The document in which the relation will be saved
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*/
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void writeXML( QDomNode& node, QDomDocument& doc ) const;
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/**
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* Set a name for this relation
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*
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* @param id
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*/
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void setRelationId( const QString& id );
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/**
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* Set a name for this relation
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*
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* @param name
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*/
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void setRelationName( const QString& name );
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/**
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* Set the referencing (child) layer id. This layer will be searched in the registry.
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*
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* @param id
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*/
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void setReferencingLayer( const QString& id );
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/**
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* Set the referenced (parent) layer id. This layer will be searched in the registry.
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*
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* @param id
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*/
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void setReferencedLayer( const QString& id );
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/**
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* Add a field pairs which is part of this relation
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* The first element of each pair are the field names of the foreign key.
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* The second element of each pair are the field names of the matching primary key.
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*
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* @param referencingField The field name on the referencing (child) layer (FK)
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* @param referencedField The field name on the referenced (parent) layer (PK)
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*/
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void addFieldPair( const QString& referencingField, const QString& referencedField );
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/**
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* Add a field pairs which is part of this relation
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* The first element of each pair are the field names of the foreign key.
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* The second element of each pair are the field names of the matching primary key.
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*
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* @param fieldPair A pair of two strings
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* @note not available in python bindings
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*/
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void addFieldPair( const FieldPair& fieldPair );
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/**
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* Creates an iterator which returns all the features on the referencing (child) layer
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* which have a foreign key pointing to the provided feature.
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*
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* @param feature A feature from the referenced (parent) layer
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*
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* @return An iterator with all the referenced features
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*/
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QgsFeatureIterator getRelatedFeatures( const QgsFeature& feature ) const;
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/**
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* Creates a request to return all the features on the referencing (child) layer
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* which have a foreign key pointing to the provided feature.
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*
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* @param feature A feature from the referenced (parent) layer
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*
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* @return A request for all the referencing features
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*/
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QgsFeatureRequest getRelatedFeaturesRequest( const QgsFeature& feature ) const;
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/**
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* Creates a request to return the feature on the referenced (parent) layer
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* which is referenced by the provided feature.
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*
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* @param attributes An attribute vector containing the foreign key
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*
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* @return A request the referenced feature
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* @note not available in python bindings
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*/
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QgsFeatureRequest getReferencedFeatureRequest( const QgsAttributes& attributes ) const;
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/**
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* Creates a request to return the feature on the referenced (parent) layer
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* which is referenced by the provided feature.
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*
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* @param feature A feature from the referencing (child) layer
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*
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* @return A request the referenced feature
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*/
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QgsFeatureRequest getReferencedFeatureRequest( const QgsFeature& feature ) const;
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/**
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* Creates a request to return the feature on the referenced (parent) layer
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* which is referenced by the provided feature.
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*
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* @param feature A feature from the referencing (child) layer
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*
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* @return A request the referenced feature
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*/
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QgsFeature getReferencedFeature( const QgsFeature& feature ) const;
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/**
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* Returns a human readable name for this relation. Mostly used as title for the children.
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*
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* @see id()
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*
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* @return A name
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*/
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QString name() const;
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/**
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* A (project-wide) unique id for this relation
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*
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* @return The id
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*/
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QString id() const;
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/**
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* Access the referencing (child) layer's id
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* This is the layer which has the field(s) which point to another layer
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*
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* @return The id of the referencing layer
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*/
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QString referencingLayerId() const;
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/**
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* Access the referencing (child) layer
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* This is the layer which has the field(s) which point to another layer
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*
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* @return The referencing layer
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*/
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QgsVectorLayer* referencingLayer() const;
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/**
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* Access the referenced (parent) layer's id
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*
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* @return The id of the referenced layer
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*/
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QString referencedLayerId() const;
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/**
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* Access the referenced (parent) layer
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*
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* @return referenced layer
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*/
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QgsVectorLayer* referencedLayer() const;
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/**
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* Returns the field pairs which form this relation
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* The first element of each pair are the field names of the foreign key.
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* The second element of each pair are the field names of the matching primary key.
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*
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* @return The fields forming the relation
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*/
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QList< FieldPair > fieldPairs() const;
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/**
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* Returns a list of attributes used to form the referenced fields
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* (most likely primary key) on the referenced (parent) layer.
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*
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* @return A list of attributes
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*/
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QgsAttributeList referencedFields() const;
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/**
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* Returns a list of attributes used to form the referencing fields
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* (foreign key) on the referencing (child) layer.
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*
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* @return A list of attributes
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*/
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QgsAttributeList referencingFields() const;
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/**
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* Returns the validity of this relation. Don't use the information if it's not valid.
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*
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* @return true if the relation is valid
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*/
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bool isValid() const;
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protected:
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/**
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* Updates the validity status of this relation.
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* Will be called internally whenever a member is changed.
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*/
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void updateRelationStatus();
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private:
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/** Unique Id */
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QString mRelationId;
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/** Human redable name*/
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QString mRelationName;
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/** The child layer */
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QString mReferencingLayerId;
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/** The child layer */
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QgsVectorLayer* mReferencingLayer;
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/** The parent layer id */
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QString mReferencedLayerId;
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/** The parent layer */
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QgsVectorLayer* mReferencedLayer;
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/** A list of fields which define the relation.
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* In most cases there will be only one value, but multiple values
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* are supported for composited foreign keys.
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* The first field is on the referencing layer, the second on the referenced */
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QList< FieldPair > mFieldPairs;
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bool mValid;
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};
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// Register QgsRelation for usage with QVariant
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Q_DECLARE_METATYPE( QgsRelation )
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#endif // QGSRELATION_H
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