app/django/contrib/gis/db/models/proxy.py
author Lennard de Rijk <ljvderijk@gmail.com>
Sat, 28 Feb 2009 13:06:04 +0000
changeset 1559 283046e54c01
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Fixed issue 205. Registered students can't apply to become an organization. If for some reason the org sign up period and student sign up period are run in parallel and a student has applied to become an org, the application will still go through the normal system. Although the student won't be able to become an org admin until he has been invalidated as a student. Patch by: Lennard de Rijk Reviewed by: to-be-reviewed

"""
 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