title: iPhone App- MkMapview get the range of area visible in map view
body: <p>in ipohne app Using mapView how to detect the the range of area visible in mapview (i mean range of longitude and latitude which binds the total area)</p>
  
  <p>and also when applying zoomin or zoomout in mapview, how to get notified that the range is changed with gesture controlled (Pinch gesture)?</p>