gis: SpatialRefSys model now uses HAS_GDAL flag, no longer uses _cach…

…e_osr(), and improved docstrings.

git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@6427 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/db/backend/postgis/__init__.py

@@ -1,5 +1,5 @@
 """
-  The PostGIS spatial database backend module.
+ The PostGIS spatial database backend module.
 """
 from django.contrib.gis.db.backend.postgis.query import \
     get_geo_where_clause, geo_quotename, \

django/contrib/gis/db/backend/postgis/creation.py

@@ -163,7 +163,7 @@ def get_spatial_db(test=False):
         return settings.DATABASE_NAME
 
 def load_postgis_sql(db_name, verbosity=1):
-    """"
+    """
     This routine loads up the PostGIS SQL files lwpostgis.sql and 
      spatial_ref_sys.sql.
     """

django/contrib/gis/models.py

@@ -1,16 +1,13 @@
+"""
+ Models for the PostGIS/OGC database tables.
+"""
 import re
 from django.db import models
 
-# Checking for the presence of GDAL
-try:
+# Checking for the presence of GDAL (needed for the SpatialReference object)
+from django.contrib.gis.gdal import HAS_GDAL
+if HAS_GDAL:
     from django.contrib.gis.gdal import SpatialReference
-    HAS_OSR = True
-except ImportError:
-    HAS_OSR = False
-
-"""
-  Models for the PostGIS/OGC database tables.
-"""
 
 # For pulling out the spheroid from the spatial reference string. This
 # regular expression is used only if the user does not have GDAL installed.
@@ -33,7 +30,9 @@ class Meta:
         db_table = 'geometry_columns'
 
     def __str__(self):
-        return "%s.%s - %dD %s field (SRID: %d)" % (self.f_table_name, self.f_geometry_column, self.coord_dimension, self.type, self.srid)
+        return "%s.%s - %dD %s field (SRID: %d)" % \
+               (self.f_table_name, self.f_geometry_column,
+                self.coord_dimension, self.type, self.srid)
 
 # This is the global 'spatial_ref_sys' table from PostGIS.
 #   See PostGIS Documentation at Ch. 4.2.1
@@ -47,41 +46,44 @@ class SpatialRefSys(models.Model):
     class Meta:
         db_table = 'spatial_ref_sys'
 
-    def _cache_osr(self):
-        "Caches a GDAL OSR SpatialReference object for this SpatialRefSys model."
-        if HAS_OSR:
-            if not hasattr(self, '_srs'):
+    @property
+    def srs(self):
+        """
+        Returns a GDAL SpatialReference object, if GDAL is installed.
+        """
+        if HAS_GDAL:
+            if hasattr(self, '_srs'):
+                # Returning a clone of the cached SpatialReference object.
+                return self._srs.clone()
+            else:
+                # Attempting to cache a SpatialReference object.
+
                 # Trying to get from WKT first
                 try:
                     self._srs = SpatialReference(self.srtext, 'wkt')
-                    return
-                except Exception, msg:
+                    return self._srs.clone()
+                except Exception, msg1:
                     pass
 
                 # Trying the proj4 text next
                 try:
                     self._srs = SpatialReference(self.proj4text, 'proj4')
-                    return
-                except Exception, msg:
+                    return self._srs.clone()
+                except Exception, msg2:
                     pass
 
-                raise Exception, 'Could not get a OSR Spatial Reference: %s' % msg
+                raise Exception, 'Could not get an OSR Spatial Reference:\n\tWKT error: %s\n\tPROJ.4 error: %s' % (msg1, msg2)
         else:
             raise Exception, 'GDAL is not installed!'
-
-    @property
-    def srs(self):
-        "Returns the SpatialReference equivalent of this model."
-        self._cache_osr()
-        return self._srs.clone()
 
     @property
     def ellipsoid(self):
-        """Returns a tuple of the ellipsoid parameters:
-        (semimajor axis, semiminor axis, and inverse flattening)."""
-        if HAS_OSR:
-            self._cache_osr()
-            return self._srs.ellipsoid
+        """
+        Returns a tuple of the ellipsoid parameters:
+        (semimajor axis, semiminor axis, and inverse flattening).
+        """
+        if HAS_GDAL:
+            return self.srs.ellipsoid
         else:
             m = spheroid_regex.match(self.srtext)
             if m: return (float(m.group('major')), float(m.group('flattening')))
@@ -90,66 +92,57 @@ def ellipsoid(self):
     @property
     def name(self):
         "Returns the projection name."
-        self._cache_osr()
-        return self._srs.name
+        return self.srs.name
 
     @property
     def spheroid(self):
         "Returns the spheroid for this spatial reference."
-        self._cache_osr()
-        return self._srs['spheroid']
+        return self.srs['spheroid']
 
     @property
     def datum(self):
         "Returns the datum for this spatial reference."
-        self._cache_osr()
-        return self._srs['datum']
+        return self.srs['datum']
 
     @property
     def projected(self):
         "Is this Spatial Reference projected?"
-        self._cache_osr()
-        return self._srs.projected
+        return self.srs.projected
 
     @property
     def local(self):
         "Is this Spatial Reference local?"
-        self._cache_osr()
-        return self._srs.local
+        return self.srs.local
 
     @property
     def geographic(self):
         "Is this Spatial Reference geographic?"
-        self._cache_osr()
-        return self._srs.geographic
+        return self.srs.geographic
 
     @property
     def linear_name(self):
         "Returns the linear units name."
-        self._cache_osr()
-        return self._srs.linear_name
+        return self.srs.linear_name
 
     @property
     def linear_units(self):
         "Returns the linear units."
-        self._cache_osr()
-        return self._srs.linear_units
+        return self.srs.linear_units
 
     @property
     def angular_units(self):
         "Returns the angular units."
-        self._cache_osr()
-        return self._srs.angular_units
+        return self.srs.angular_units
 
     @property
     def angular_name(self):
         "Returns the name of the angular units."
-        self._cache_osr()
-        return self._srs.angular_name
+        return self.srs.angular_name
 
     def __str__(self):
-        "Returns the string representation.  If GDAL is installed, it will be 'pretty' OGC WKT."
-        if HAS_OSR:
-            self._cache_osr()
-            if hasattr(self, '_srs'): return str(self._srs)
-        return "%d:%s " % (self.srid, self.auth_name)
+        """
+        Returns the string representation.  If GDAL is installed,
+        it will be 'pretty' OGC WKT.
+        """
+        if HAS_GDAL: return str(self.srs)
+        else: return "%d:%s " % (self.srid, self.auth_name)