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from django import forms
from django.utils.translation import ugettext_lazy as _
# While this couples the geographic forms to the GEOS library,
# it decouples from database (by not importing SpatialBackend).
from django.contrib.gis.geos import GEOSGeometry
class GeometryField(forms.Field):
"""
This is the basic form field for a Geometry. Any textual input that is
accepted by GEOSGeometry is accepted by this form. By default,
this includes WKT, HEXEWKB, WKB (in a buffer), and GeoJSON.
"""
widget = forms.Textarea
default_error_messages = {
'no_geom' : _(u'No geometry value provided.'),
'invalid_geom' : _(u'Invalid geometry value.'),
'invalid_geom_type' : _(u'Invalid geometry type.'),
'transform_error' : _(u'An error occurred when transforming the geometry '
'to the SRID of the geometry form field.'),
}
def __init__(self, **kwargs):
# Pop out attributes from the database field, or use sensible
# defaults (e.g., allow None).
self.srid = kwargs.pop('srid', None)
self.geom_type = kwargs.pop('geom_type', 'GEOMETRY')
self.null = kwargs.pop('null', True)
super(GeometryField, self).__init__(**kwargs)
def clean(self, value):
"""
Validates that the input value can be converted to a Geometry
object (which is returned). A ValidationError is raised if
the value cannot be instantiated as a Geometry.
"""
if not value:
if self.null and not self.required:
# The geometry column allows NULL and is not required.
return None
else:
raise forms.ValidationError(self.error_messages['no_geom'])
# Trying to create a Geometry object from the form value.
try:
geom = GEOSGeometry(value)
except:
raise forms.ValidationError(self.error_messages['invalid_geom'])
# Ensuring that the geometry is of the correct type (indicated
# using the OGC string label).
if str(geom.geom_type).upper() != self.geom_type and not self.geom_type == 'GEOMETRY':
raise forms.ValidationError(self.error_messages['invalid_geom_type'])
# Transforming the geometry if the SRID was set.
if self.srid:
if not geom.srid:
# Should match that of the field if not given.
geom.srid = self.srid
elif self.srid != -1 and self.srid != geom.srid:
try:
geom.transform(self.srid)
except:
raise forms.ValidationError(self.error_messages['transform_error'])
return geom
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