qgis/QGIS — pull request #1494 by m-kuhn (2014-06-30 16:22:55+00:00)
Title: [FEATURE] Expression field (Virtual field)

This adds the possibility to create virtual fields based on an expression.
In contrast to a field calculated with the field calculator such a field is calculated on the fly and will resolve to a different value when data on the underlying feature changes.