class QgsExpressionFieldBuffer
{
%TypeHeaderCode
#include <qgsexpressionfieldbuffer.h>
%End
  public:
    class ExpressionField
    {
      ExpressionField();
      ExpressionField( const QString &exp, const QgsField &fld );
    };

    QgsExpressionFieldBuffer();

    /**
     * Add an expression to the buffer
     *
     * @param exp expression to add
     * @param fld field to add
     */
    void addExpression( const QString &exp, const QgsField &fld );

    /**
     * Remove an expression from the buffer
     *
     * @param index index of expression to remove
     */
    void removeExpression( int index );

    /**
     * Renames an expression field at a given index
     *
     * @param index The index of the expression to change
     * @param name   New name for field
     *
     * @note added in 3.0
     */
    void renameExpression( int index, const QString &name );

    /**
     * Changes the expression at a given index
     *
     * @param index The index of the expression to change
     * @param exp   The new expression to set
     *
     * @note added in 2.9
     */
    void updateExpression( int index, const QString &exp );

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

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

    /**
     * Adds fields with the expressions buffered in this object to a QgsFields object
     *
     * @param flds The fields to be updated
     */
    void updateFields( QgsFields &flds );

    QList<QgsExpressionFieldBuffer::ExpressionField> expressions() const;
};