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