1 from django import forms

     2 from django.utils.translation import ugettext_lazy as _

     3 

     4 # While this couples the geographic forms to the GEOS library,

     5 # it decouples from database (by not importing SpatialBackend).

     6 from django.contrib.gis.geos import GEOSGeometry

     7 

     8 class GeometryField(forms.Field):

     9     """

    10     This is the basic form field for a Geometry.  Any textual input that is

    11     accepted by GEOSGeometry is accepted by this form.  By default,

    12     this includes WKT, HEXEWKB, WKB (in a buffer), and GeoJSON.

    13     """

    14     widget = forms.Textarea

    15 

    16     default_error_messages = {

    17         'no_geom' : _(u'No geometry value provided.'),

    18         'invalid_geom' : _(u'Invalid geometry value.'),

    19         'invalid_geom_type' : _(u'Invalid geometry type.'),

    20         'transform_error' : _(u'An error occurred when transforming the geometry '

    21                               'to the SRID of the geometry form field.'),

    22         }

    23 

    24     def __init__(self, **kwargs):

    25         # Pop out attributes from the database field, or use sensible

    26         # defaults (e.g., allow None).

    27         self.srid = kwargs.pop('srid', None)

    28         self.geom_type = kwargs.pop('geom_type', 'GEOMETRY')

    29         self.null = kwargs.pop('null', True)

    30         super(GeometryField, self).__init__(**kwargs)

    31 

    32     def clean(self, value):

    33         """

    34         Validates that the input value can be converted to a Geometry

    35         object (which is returned).  A ValidationError is raised if

    36         the value cannot be instantiated as a Geometry.

    37         """

    38         if not value:

    39             if self.null and not self.required:

    40                 # The geometry column allows NULL and is not required.

    41                 return None

    42             else:

    43                 raise forms.ValidationError(self.error_messages['no_geom'])

    44 

    45         # Trying to create a Geometry object from the form value.

    46         try:

    47             geom = GEOSGeometry(value)

    48         except:

    49             raise forms.ValidationError(self.error_messages['invalid_geom'])

    50 

    51         # Ensuring that the geometry is of the correct type (indicated

    52         # using the OGC string label).

    53         if str(geom.geom_type).upper() != self.geom_type and not self.geom_type == 'GEOMETRY':

    54             raise forms.ValidationError(self.error_messages['invalid_geom_type'])

    55 

    56         # Transforming the geometry if the SRID was set.

    57         if self.srid:

    58             if not geom.srid:

    59                 # Should match that of the field if not given.

    60                 geom.srid = self.srid

    61             elif self.srid != -1 and self.srid != geom.srid:

    62                 try:

    63                     geom.transform(self.srid)

    64                 except:

    65                     raise forms.ValidationError(self.error_messages['transform_error'])

    66 

    67         return geom