Ticket #9448: layer_reference_ds.diff

django/contrib/gis/tests/test_gdal_ds.py

@@ -130 +130 @@
             control_vals = source.field_values[fld_name][sl]
             self.assertEqual(control_vals, test_vals)
 
+    def test03c_layer_references(self):
+        "Test to make sure Layer access is still available without the DataSource."
+        source = ds_list[0]
+
+        # See ticket #9448.
+        def get_layer():
+            # This DataSource object is not accessible outside this
+            # scope.  However, a reference should still be kept alive
+            # on the `Layer` returned.
+            ds = DataSource(source.ds)
+            return ds[0]
+
+        # Making sure we can call OGR routines on the Layer returned.
+        lyr = get_layer()
+        self.assertEqual(source.nfeat, len(lyr))
+        self.assertEqual(source.gtype, lyr.geom_type.num)        
+
     def test04_features(self):
         "Testing Data Source Features."
         for source in ds_list:

django/contrib/gis/gdal/datasource.py

@@ -111 +111 @@
             l = get_layer(self._ptr, index)
         else:
             raise TypeError('Invalid index type: %s' % type(index))
-        return Layer(l)
+        return Layer(l, self)
         
     def __len__(self):
         "Returns the number of layers within the data source."

django/contrib/gis/gdal/layer.py

@@ -25 +25 @@
     "A class that wraps an OGR Layer, needs to be instantiated from a DataSource object."
 
     #### Python 'magic' routines ####
-    def __init__(self, layer_ptr):
-        "Needs a C pointer (Python/ctypes integer) in order to initialize."
+    def __init__(self, layer_ptr, ds):
+        """
+        Initializes on an OGR C pointer and the `DataSource` object that 
+        owns this layer.  The `DataSource` object is required so that
+        a reference to it is kept with this Layer.  This prevents the 
+        garbage collection of the `DataSource` while this `Layer` object
+        is still active.
+        """
         self._ptr = None # Initially NULL
         if not layer_ptr:
             raise OGRException('Cannot create Layer, invalid pointer given')
         self._ptr = layer_ptr
+        self._ds = ds
         self._ldefn = get_layer_defn(self._ptr)
         # Does the Layer support random reading?
         self._random_read = self.test_capability('RandomRead')