gis: Added the ogrinspect module (via patch from tlp), which provides utilities for the generation of GeoDjango models from OGR data sources as well as generation of LayerMapping dictionaries.

git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@6688 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/utils/__init__.py

@@ -1,15 +1,19 @@
 """
  This module contains useful utilities for GeoDjango.
 """
-
-# Importing LayerMapping and ogrinfo (will not be done if GDAL is not
-#  installed)
+# Importing the utilities that depend on GDAL, if available.
 from django.contrib.gis.gdal import HAS_GDAL
 if HAS_GDAL:
     from django.contrib.gis.utils.ogrinfo import ogrinfo, sample
-    from django.contrib.gis.utils.layermapping import LayerMapping
+    from django.contrib.gis.utils.ogrinspect import mapping, ogrinspect
+    try:
+        # LayerMapping requires DJANGO_SETTINGS_MODULE to be set, 
+        # so this needs to be in try/except.
+        from django.contrib.gis.utils.layermapping import LayerMapping
+    except:
+        pass
     
-# Importing GeoIP
+# Attempting to import the GeoIP class.
 try:
     from django.contrib.gis.utils.geoip import GeoIP
     HAS_GEOIP = True

django/contrib/gis/utils/ogrinspect.py

@@ -0,0 +1,125 @@
+"""
+ This module is for inspecting OGR data sources and generating either
+ models for GeoDjango and/or mapping dictionaries for use with the
+ LayerMapping utility.
+
+ Author: Travis Pinney
+"""
+
+# Requires GDAL to use.
+from django.contrib.gis.gdal import DataSource
+
+def mapping(data_source, geom_name='geom', layer_key=0):
+    """
+    Given a DataSource, generates a dictionary that may be used 
+    for invoking the LayerMapping utility.
+
+    Keyword Arguments:
+     `geom_name` => The name of the geometry field to use for the model.
+
+     `layer_key` => The key for specifying which layer in the DataSource to use;
+       defaults to 0 (the first layer).  May be an integer index or a string
+       identifier for the layer.
+    """
+    if isinstance(data_source, basestring):
+        # Instantiating the DataSource from the string.
+        data_source = DataSource(data_source)
+    elif isinstance(data_source, DataSource):
+        pass
+    else:
+        raise TypeError('Data source parameter must be a string or a DataSource object.')
+    
+    # Creating the dictionary.
+    _mapping = {}
+
+    # Generating the field name for each field in the layer.
+    for field in data_source[layer_key].fields:
+        mfield = field.lower()
+        if mfield[-1:] == '_': mfield += 'field'
+        _mapping[mfield] = field
+    gtype = data_source[layer_key].geom_type
+    _mapping[geom_name] = str(gtype).upper()
+
+    return _mapping
+
+def ogrinspect(*args, **kwargs):
+    """
+    Given a data source (either a string or a DataSource object) and a string
+    model name this function will generate a GeoDjango model.
+
+    Keyword Arguments
+     `geom_name` => For specifying the model name for the Geometry Field.
+
+     `layer_key` => The key for specifying which layer in the DataSource to use;
+       defaults to 0 (the first layer).  May be an integer index or a string
+       identifier for the layer.
+
+     `srid` => The SRID to use for the Geometry Field.  If it can be determined,
+       the SRID of the datasource
+
+    Note: This routine calls the _ogrinspect() helper to do the heavy lifting.
+    """
+    return '\n'.join(s for s in _ogrinspect(*args, **kwargs))
+
+def _ogrinspect(data_source, model_name, geom_name='geom', layer_key=0, srid=None):
+    """
+    Helper routine for `ogrinspect` that generates GeoDjango models corresponding
+    to the given data source.  See the `ogrinspect` docstring for more details.
+    """
+
+    # Getting the DataSource
+    if isinstance(data_source, str):
+        data_source = DataSource(data_source)
+    elif isinstance(data_source, DataSource):
+        pass
+    else:
+        raise TypeError('Data source parameter must be a string or a DataSource object.')
+
+    yield '# This is an auto-generated Django model module created by ogrinspect.'
+    yield 'from django.contrib.gis.db import models'
+    yield ''
+    yield 'class %s(models.Model):' % model_name
+    
+    layer = data_source[layer_key]        
+    
+    for width, precision, field in zip(layer.field_widths, layer.field_precisions, layer.fields):
+        feature = layer[0]
+        fld_type = feature[field].type_name
+        mfield = field.lower()
+        
+        if mfield[-1:] == '_':
+            mfield += 'field'
+        
+        if fld_type == 'Real':
+            yield '    %s = models.DecimalField(max_digits=%s, decimal_places=%s)' % (mfield, width, precision)
+        elif fld_type == 'Integer':
+            yield '    %s = models.IntegerField()' % mfield
+        elif fld_type == 'String':
+            yield '    %s = models.CharField(max_length=%s)' % (mfield, width)
+        elif fld_type == 'Date':
+            yield '    %s = models.DateField()' % mfield
+        elif fld_type == 'DateTime':
+            yield '    %s = models.DateTimeField()' % mfield
+        elif fld_type == 'Time':
+            yield '    %s = models.TimeField()' % mfield
+        else:
+            raise Exception('Unknown field type %s in %s' % (fld_type, mfield))
+    
+    # Getting the geometry type
+    gtype = layer.geom_type
+    
+    # Setting up the SRID parameter string.
+    if srid is None:
+        srid = layer.srs.srid
+        if srid is None:
+            srid_str = 'srid=-1'
+        elif srid == 4326:
+            # WGS84 is the default.
+            srid_str = ''
+        else:
+            srid_str = 'srid=%s' % srid
+    else:
+        srid_str = 'srid=%s' % srid
+
+    yield '    %s = models.%s(%s)' % (geom_name, gtype.django, srid_str)
+    yield '    objects = models.GeoManager()'