gis: gdal: fixed area function, place field pointer within class, integer and float fields return None when empty.

git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@5754 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/gdal/field.py

@@ -10,11 +10,11 @@ from django.contrib.gis.gdal.error import OGRException
 class Field(object):
     "A class that wraps an OGR Field, needs to be instantiated from a Feature object."
 
-    _fld = 0 # Initially NULL
-
     #### Python 'magic' routines ####
     def __init__(self, fld, val=''):
         "Needs a C pointer (Python integer in ctypes) in order to initialize."
+        self._fld = 0 # Initially NULL
+
         if not fld:
             raise OGRException, 'Cannot create OGR Field, invalid pointer given.'
         self._fld = fld
@@ -51,23 +51,19 @@ class OFTInteger(Field):
         try:
             return int(self._val)
         except ValueError:
-            return 0
-    
+            return None
 class OFTIntegerList(Field): pass
+
 class OFTReal(Field):
     @property
     def value(self):
         "Returns a float contained in this field."
-
         try:
             return float(self._val)
         except ValueError:
-            #FIXME: 0?  None?
-            return 0
-
-        
-
+            return None
 class OFTRealList(Field): pass
+
 class OFTString(Field): pass
 class OFTStringList(Field): pass
 class OFTWideString(Field): pass

django/contrib/gis/gdal/geometries.py

@@ -55,16 +55,22 @@ from django.contrib.gis.gdal.srs import SpatialReference, CoordTransform
 #
 # The OGR_G_* routines are relevant here.
 
-#### ctypes prototypes ####
+#### ctypes prototypes for functions that return double values ####
 def pnt_func(f):
     "For accessing point information."
     f.restype = c_double
     f.argtypes = [c_void_p, c_int]
     return f
+# GetX, GetY, GetZ all return doubles.
 getx = pnt_func(lgdal.OGR_G_GetX)
 gety = pnt_func(lgdal.OGR_G_GetY)
 getz = pnt_func(lgdal.OGR_G_GetZ)
 
+# GetArea returns a double.
+get_area = lgdal.OGR_G_GetArea
+get_area.restype = c_double
+get_area.argtypes = [c_void_p]
+
 #### OGRGeometry Class ####
 class OGRGeometryIndexError(OGRException, KeyError):
     """This exception is raised when an invalid index is encountered, and has
@@ -211,8 +217,7 @@ class OGRGeometry(object):
     @property
     def area(self):
         "Returns the area for a LinearRing, Polygon, or MultiPolygon; 0 otherwise."
-        a = lgdal.OGR_G_GetArea(self._g)
-        return a.value
+        return get_area(self._g)
 
     @property
     def envelope(self):