Fixed django#18640 -- Allowed access to GDAL Feature without Datasource

Thanks Justin Bronn for improving my initial patch.

django/contrib/gis/gdal/feature.py

@@ -16,15 +16,21 @@
 #
 # The OGR_F_* routines are relevant here.
 class Feature(GDALBase):
-    "A class that wraps an OGR Feature, needs to be instantiated from a Layer object."
+    """
+    This class that wraps an OGR Feature, needs to be instantiated
+    from a Layer object.
+    """
 
     #### Python 'magic' routines ####
-    def __init__(self, feat, fdefn):
-        "Initializes on the pointers for the feature and the layer definition."
-        if not feat or not fdefn:
+    def __init__(self, feat, layer):
+        """
+        Initializes on the feature pointers for the feature and the layer
+        definition, as well as the Layer.
+        """
+        if not feat:
             raise OGRException('Cannot create OGR Feature, invalid pointer given.')
         self.ptr = feat
-        self._fdefn = fdefn
+        self._layer = layer
 
     def __del__(self):
         "Releases a reference to this object."
@@ -43,7 +49,7 @@ def __getitem__(self, index):
             if index < 0 or index > self.num_fields:
                 raise OGRIndexError('index out of range')
             i = index
-        return Field(self.ptr, i)
+        return Field(self, i)
 
     def __iter__(self):
         "Iterates over each field in the Feature."
@@ -71,7 +77,7 @@ def fid(self):
     @property
     def layer_name(self):
         "Returns the name of the layer for the feature."
-        return capi.get_feat_name(self._fdefn)
+        return capi.get_feat_name(self._layer._ldefn)
 
     @property
     def num_fields(self):
@@ -81,7 +87,7 @@ def num_fields(self):
     @property
     def fields(self):
         "Returns a list of fields in the Feature."
-        return [capi.get_field_name(capi.get_field_defn(self._fdefn, i))
+        return [capi.get_field_name(capi.get_field_defn(self._layer._ldefn, i))
                 for i in xrange(self.num_fields)]
 
     @property
@@ -94,7 +100,7 @@ def geom(self):
     @property
     def geom_type(self):
         "Returns the OGR Geometry Type for this Feture."
-        return OGRGeomType(capi.get_fd_geom_type(self._fdefn))
+        return OGRGeomType(capi.get_fd_geom_type(self._layer._ldefn))
 
     #### Feature Methods ####
     def get(self, field):

django/contrib/gis/gdal/field.py

@@ -9,20 +9,23 @@
 #
 # The OGR_Fld_* routines are relevant here.
 class Field(GDALBase):
-    "A class that wraps an OGR Field, needs to be instantiated from a Feature object."
+    """
+    This class wraps an OGR Field, and needs to be instantiated
+    from a Feature object.
+    """
 
     #### Python 'magic' routines ####
     def __init__(self, feat, index):
         """
-        Initializes on the feature pointer and the integer index of
+        Initializes on the feature object and the integer index of
         the field within the feature.
         """
         # Setting the feature pointer and index.
         self._feat = feat
         self._index = index
 
         # Getting the pointer for this field.
-        fld_ptr = capi.get_feat_field_defn(feat, index)
+        fld_ptr = capi.get_feat_field_defn(feat.ptr, index)
         if not fld_ptr:
             raise OGRException('Cannot create OGR Field, invalid pointer given.')
         self.ptr = fld_ptr
@@ -42,21 +45,22 @@ def __str__(self):
     #### Field Methods ####
     def as_double(self):
         "Retrieves the Field's value as a double (float)."
-        return capi.get_field_as_double(self._feat, self._index)
+        return capi.get_field_as_double(self._feat.ptr, self._index)
 
     def as_int(self):
         "Retrieves the Field's value as an integer."
-        return capi.get_field_as_integer(self._feat, self._index)
+        return capi.get_field_as_integer(self._feat.ptr, self._index)
 
     def as_string(self):
         "Retrieves the Field's value as a string."
-        return capi.get_field_as_string(self._feat, self._index)
+        return capi.get_field_as_string(self._feat.ptr, self._index)
 
     def as_datetime(self):
         "Retrieves the Field's value as a tuple of date & time components."
         yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)]
-        status = capi.get_field_as_datetime(self._feat, self._index, byref(yy), byref(mm), byref(dd),
-                                            byref(hh), byref(mn), byref(ss), byref(tz))
+        status = capi.get_field_as_datetime(
+            self._feat.ptr, self._index, byref(yy), byref(mm), byref(dd),
+            byref(hh), byref(mn), byref(ss), byref(tz))
         if status:
             return (yy, mm, dd, hh, mn, ss, tz)
         else:

django/contrib/gis/gdal/layer.py

@@ -61,7 +61,7 @@ def __iter__(self):
         # ResetReading() must be called before iteration is to begin.
         capi.reset_reading(self._ptr)
         for i in xrange(self.num_feat):
-            yield Feature(capi.get_next_feature(self._ptr), self._ldefn)
+            yield Feature(capi.get_next_feature(self._ptr), self)
 
     def __len__(self):
         "The length is the number of features."
@@ -81,7 +81,7 @@ def _make_feature(self, feat_id):
         if self._random_read:
             # If the Layer supports random reading, return.
             try:
-                return Feature(capi.get_feature(self.ptr, feat_id), self._ldefn)
+                return Feature(capi.get_feature(self.ptr, feat_id), self)
             except OGRException:
                 pass
         else:

django/contrib/gis/gdal/tests/test_ds.py

@@ -125,7 +125,10 @@ def test03b_layer_slice(self):
             self.assertEqual(control_vals, test_vals)
 
     def test03c_layer_references(self):
-        "Test to make sure Layer access is still available without the DataSource."
+        """
+        Test to make sure Layer/Feature access is still available without
+        the DataSource/Feature.
+        """
         source = ds_list[0]
 
         # See ticket #9448.
@@ -141,6 +144,9 @@ def get_layer():
         self.assertEqual(source.nfeat, len(lyr))
         self.assertEqual(source.gtype, lyr.geom_type.num)
 
+        # Same issue for Feature/Field objects, see #18640
+        self.assertEqual(str(lyr[0]['str']), "1")
+
     def test04_features(self):
         "Testing Data Source Features."
         for source in ds_list: