title: Get current index from an item in a QAbstractItemModel
body: <p>I have a Model/Item based design, similar to the one explained at <a href="http://qt-project.org/forums/viewthread/14121" rel="nofollow">http://qt-project.org/forums/viewthread/14121</a></p>
  
  <p>What I really need is a method like RosterElement::currentIndex() which returns a QModelIndex object.
  But I have no idea how to get the index without checking all indicies internalPointer() values against <strong>this</strong> (there should be only one single match, haven't tried it yet).
  Are there any better implementations?</p>