|
0
|
1 |
""" |
|
29
|
2 |
The GeometryProxy object, allows for lazy-geometries. The proxy uses |
|
|
3 |
Python descriptors for instantiating and setting Geometry objects |
|
|
4 |
corresponding to geographic model fields. |
|
0
|
5 |
|
|
29
|
6 |
Thanks to Robert Coup for providing this functionality (see #4322). |
|
0
|
7 |
""" |
|
|
8 |
|
|
29
|
9 |
class GeometryProxy(object): |
|
|
10 |
def __init__(self, klass, field): |
|
0
|
11 |
""" |
|
29
|
12 |
Proxy initializes on the given Geometry class (not an instance) and |
|
0
|
13 |
the GeometryField. |
|
|
14 |
""" |
|
29
|
15 |
self._field = field |
|
0
|
16 |
self._klass = klass |
|
29
|
17 |
|
|
|
18 |
def __get__(self, obj, type=None): |
|
0
|
19 |
""" |
|
|
20 |
This accessor retrieves the geometry, initializing it using the geometry |
|
29
|
21 |
class specified during initialization and the HEXEWKB value of the field. |
|
0
|
22 |
Currently, only GEOS or OGR geometries are supported. |
|
|
23 |
""" |
|
29
|
24 |
if obj is None: |
|
|
25 |
# Accessed on a class, not an instance |
|
|
26 |
return self |
|
|
27 |
|
|
0
|
28 |
# Getting the value of the field. |
|
29
|
29 |
geom_value = obj.__dict__[self._field.attname] |
|
|
30 |
|
|
|
31 |
if isinstance(geom_value, self._klass): |
|
0
|
32 |
geom = geom_value |
|
|
33 |
elif (geom_value is None) or (geom_value==''): |
|
|
34 |
geom = None |
|
29
|
35 |
else: |
|
0
|
36 |
# Otherwise, a Geometry object is built using the field's contents, |
|
|
37 |
# and the model's corresponding attribute is set. |
|
|
38 |
geom = self._klass(geom_value) |
|
29
|
39 |
setattr(obj, self._field.attname, geom) |
|
|
40 |
return geom |
|
|
41 |
|
|
0
|
42 |
def __set__(self, obj, value): |
|
|
43 |
""" |
|
|
44 |
This accessor sets the proxied geometry with the geometry class |
|
|
45 |
specified during initialization. Values of None, HEXEWKB, or WKT may |
|
|
46 |
be used to set the geometry as well. |
|
|
47 |
""" |
|
|
48 |
# The OGC Geometry type of the field. |
|
|
49 |
gtype = self._field.geom_type |
|
29
|
50 |
|
|
0
|
51 |
# The geometry type must match that of the field -- unless the |
|
|
52 |
# general GeometryField is used. |
|
|
53 |
if isinstance(value, self._klass) and (str(value.geom_type).upper() == gtype or gtype == 'GEOMETRY'): |
|
|
54 |
# Assigning the SRID to the geometry. |
|
|
55 |
if value.srid is None: value.srid = self._field.srid |
|
29
|
56 |
elif value is None or isinstance(value, (basestring, buffer)): |
|
|
57 |
# Set with None, WKT, HEX, or WKB |
|
0
|
58 |
pass |
|
|
59 |
else: |
|
|
60 |
raise TypeError('cannot set %s GeometryProxy with value of type: %s' % (obj.__class__.__name__, type(value))) |
|
|
61 |
|
|
|
62 |
# Setting the objects dictionary with the value, and returning. |
|
29
|
63 |
obj.__dict__[self._field.attname] = value |
|
|
64 |
return value |