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Diffstat (limited to 'webapp/django/contrib/gis/db/models/proxy.py')
-rw-r--r-- | webapp/django/contrib/gis/db/models/proxy.py | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/webapp/django/contrib/gis/db/models/proxy.py b/webapp/django/contrib/gis/db/models/proxy.py new file mode 100644 index 0000000000..34276a6d63 --- /dev/null +++ b/webapp/django/contrib/gis/db/models/proxy.py @@ -0,0 +1,62 @@ +""" + 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 |