+
−"""
+
− The GeometryProxy object, allows for lazy-geometries.  The proxy uses
+
− Python descriptors for instantiating and setting Geometry objects
+
− corresponding to geographic model fields.
+
−
+
− Thanks to Robert Coup for providing this functionality (see #4322).
+
−"""
+
−
+
−from types import NoneType, StringType, UnicodeType
+
−
+
−class GeometryProxy(object): 
+
−    def __init__(self, klass, field): 
+
−        """
+
−        Proxy initializes on the given Geometry class (not an instance) and 
+
−        the GeometryField.
+
−        """
+
−        self._field = field 
+
−        self._klass = klass
+
−     
+
−    def __get__(self, obj, type=None): 
+
−        """
+
−        This accessor retrieves the geometry, initializing it using the geometry
+
−        class specified during initialization and the HEXEWKB value of the field.  
+
−        Currently, only GEOS or OGR geometries are supported.
+
−        """
+
−        # Getting the value of the field.
+
−        geom_value = obj.__dict__[self._field.attname] 
+
−        
+
−        if isinstance(geom_value, self._klass): 
+
−            geom = geom_value
+
−        elif (geom_value is None) or (geom_value==''):
+
−            geom = None
+
−        else: 
+
−            # Otherwise, a Geometry object is built using the field's contents,
+
−            # and the model's corresponding attribute is set.
+
−            geom = self._klass(geom_value)
+
−            setattr(obj, self._field.attname, geom) 
+
−        return geom 
+
−     
+
−    def __set__(self, obj, value):
+
−        """
+
−        This accessor sets the proxied geometry with the geometry class
+
−        specified during initialization.  Values of None, HEXEWKB, or WKT may
+
−        be used to set the geometry as well.
+
−        """
+
−        # The OGC Geometry type of the field.
+
−        gtype = self._field._geom
+
−        
+
−        # The geometry type must match that of the field -- unless the
+
−        # general GeometryField is used.
+
−        if isinstance(value, self._klass) and (str(value.geom_type).upper() == gtype or gtype == 'GEOMETRY'):
+
−            # Assigning the SRID to the geometry.
+
−            if value.srid is None: value.srid = self._field._srid
+
−        elif isinstance(value, (NoneType, StringType, UnicodeType)):
+
−            # Set with None, WKT, or HEX
+
−            pass
+
−        else:
+
−            raise TypeError('cannot set %s GeometryProxy with value of type: %s' % (obj.__class__.__name__, type(value)))
+
−
+
−        # Setting the objects dictionary with the value, and returning.
+
−        obj.__dict__[self._field.attname] = value 
+
−        return value