class QgsVectorLayerJoinBuffer : QObject
{
%TypeHeaderCode
#include <qgsvectorlayerjoinbuffer.h>
%End
  public:
    QgsVectorLayerJoinBuffer( QgsVectorLayer* layer = 0 );
    ~QgsVectorLayerJoinBuffer();

    /** Joins another vector layer to this layer
      @param joinInfo join object containing join layer id, target and source field
      @return (since 2.6) whether the join was successfully added */
    bool addJoin( const QgsVectorJoinInfo& joinInfo );

    /** Removes a vector layer join
      @returns true if join was found and successfully removed */
    bool removeJoin( const QString& joinLayerId );

    /** Updates field map with joined attributes
      @param fields map to append joined attributes
     */
    void updateFields( QgsFields& fields );

    /** Calls cacheJoinLayer() for all vector joins*/
    void createJoinCaches();

    /** Saves mVectorJoins to xml under the layer node*/
    void writeXml( QDomNode& layer_node, QDomDocument& document ) const;

    /** Reads joins from project file*/
    void readXml( const QDomNode& layer_node );

    /** Quick way to test if there is any join at all*/
    bool containsJoins() const;

    const QList< QgsVectorJoinInfo >& vectorJoins() const;

    /** Finds the vector join for a layer field index.
      @param index this layers attribute index
      @param fields fields of the vector layer (including joined fields)
      @param sourceFieldIndex Output: field's index in source layer */
    const QgsVectorJoinInfo* joinForFieldIndex( int index, const QgsFields& fields, int& sourceFieldIndex /Out/ ) const;

    //! Find out what is the first index of the join within fields. Returns -1 if join is not present
    //! @note added in 2.6
    int joinedFieldsOffset( const QgsVectorJoinInfo* info, const QgsFields& fields );

    //! Return a vector of indices for use in join based on field names from the layer
    //! @note added in 2.6
    static QVector<int> joinSubsetIndices( QgsVectorLayer* joinLayer, const QStringList& joinFieldsSubset );

    //! Create a copy of the join buffer
    //! @note added in 2.6
    QgsVectorLayerJoinBuffer* clone() const /Factory/;

  signals:
    //! Emitted whenever the list of joined fields changes (e.g. added join or joined layer's fields change)
    //! @note added in 2.6
    void joinedFieldsChanged();
};