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Enso-Bot/venv/Lib/site-packages/django/contrib/gis/db/models/proxy.py

80 lines
3.0 KiB
Python

"""
The SpatialProxy object allows for lazy-geometries and lazy-rasters. The proxy
uses Python descriptors for instantiating and setting Geometry or Raster
objects corresponding to geographic model fields.
Thanks to Robert Coup for providing this functionality (see #4322).
"""
from django.db.models.query_utils import DeferredAttribute
class SpatialProxy(DeferredAttribute):
def __init__(self, klass, field, load_func=None):
"""
Initialize on the given Geometry or Raster class (not an instance)
and the corresponding field.
"""
self._klass = klass
self._load_func = load_func or klass
super().__init__(field)
def __get__(self, instance, cls=None):
"""
Retrieve the geometry or raster, initializing it using the
corresponding class specified during initialization and the value of
the field. Currently, GEOS or OGR geometries as well as GDALRasters are
supported.
"""
if instance is None:
# Accessed on a class, not an instance
return self
# Getting the value of the field.
try:
geo_value = instance.__dict__[self.field.attname]
except KeyError:
geo_value = super().__get__(instance, cls)
if isinstance(geo_value, self._klass):
geo_obj = geo_value
elif (geo_value is None) or (geo_value == ''):
geo_obj = None
else:
# Otherwise, a geometry or raster object is built using the field's
# contents, and the model's corresponding attribute is set.
geo_obj = self._load_func(geo_value)
setattr(instance, self.field.attname, geo_obj)
return geo_obj
def __set__(self, instance, value):
"""
Retrieve the proxied geometry or raster with the corresponding class
specified during initialization.
To set geometries, use values of None, HEXEWKB, or WKT.
To set rasters, use JSON or dict values.
"""
# The geographic type of the field.
gtype = self.field.geom_type
if gtype == 'RASTER' and (value is None or isinstance(value, (str, dict, self._klass))):
# For raster fields, assure input is None or a string, dict, or
# raster instance.
pass
elif isinstance(value, self._klass):
# The geometry type must match that of the field -- unless the
# general GeometryField is used.
if value.srid is None:
# Assigning the field SRID if the geometry has no SRID.
value.srid = self.field.srid
elif value is None or isinstance(value, (str, memoryview)):
# Set geometries with None, WKT, HEX, or WKB
pass
else:
raise TypeError('Cannot set %s SpatialProxy (%s) with value of type: %s' % (
instance.__class__.__name__, gtype, type(value)))
# Setting the objects dictionary with the value, and returning.
instance.__dict__[self.field.attname] = value
return value