Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
branch: master
145 lines (116 sloc) 5.038 kb
from sqlalchemy.orm.util import class_mapper
from sqlalchemy.orm.properties import ColumnProperty
from geoalchemy2.types import Geometry
from geoalchemy2.shape import from_shape, to_shape
import geojson
from shapely.geometry import asShape
class GeoInterface(object):
"""
Base class for SQLAlchemy/GeoAlchemy mapped classes. Using this class
mapped objects implement the Python Geo Interface (``__geo_interface__``)
and expose ``__init__`` and ``__update__`` functions as needed for use with
:py:class:`papyrus.protocol.Protocol`.
Using the class is optional, and implementing its own
``__geo_interface__``, ``__init__`` and ``__update__`` functions in its
mapped classes is another option.
This class can be used as the base class of the user-defined class.
Example::
class Spot(GeoInterface, Base):
__tablename__ = 'spots'
id = Column(Integer, primary_key=True)
geom = Column('the_geom', Geometry('POINT', 4326))
Or as the base class of classes generated by SQLAlchemy's declarative
layer. Example::
# constructor=None is required for declarative_base to not
# provide its own __init__ constructor
Base = declarative_base(cls=GeoInterface, constructor=None)
class Spot(Base):
__tablename__ = 'spots'
id = Column(Integer, primary_key=True)
geom = Geometry('the_geom', Geometry('POINT', 4326))
"""
__add_properties__ = None
"""
Use this property to make :py:meth:`.__read__` and :py:meth:`.__update__`
read from, and write to, additional properties. By default column
properties only are considered. Default is ``None``.
Example::
class Spot(Base):
__tablename__ = 'spots'
id = Column(Integer, primary_key=True)
geom = Column('the_geom', Geometry('POINT', 4326))
type_id = Column(Integer, ForeignKey('spot_type.id')
type_ = relationship(SpotType)
type = association_proxy('type_', 'type')
__add_properties__ = ('type',)
"""
def __init__(self, feature=None):
"""
Called by the protocol on object creation.
Arguments:
* ``feature`` The GeoJSON feature as received from the client.
"""
if feature:
for p in class_mapper(self.__class__).iterate_properties:
if not isinstance(p, ColumnProperty):
continue
if p.columns[0].primary_key:
primary_key = p.key
setattr(self, primary_key, feature.id)
self.__update__(feature)
def __update__(self, feature):
"""
Called by the protocol on object update.
Arguments:
* ``feature`` The GeoJSON feature as received from the client.
"""
for p in class_mapper(self.__class__).iterate_properties:
if not isinstance(p, ColumnProperty):
continue
col = p.columns[0]
if isinstance(col.type, Geometry):
geom = feature.geometry
if geom and not isinstance(geom, geojson.geometry.Default):
srid = col.type.srid
shape = asShape(geom)
setattr(self, p.key, from_shape(shape, srid=srid))
self._shape = shape
elif not col.primary_key:
if p.key in feature.properties:
setattr(self, p.key, feature.properties[p.key])
if self.__add_properties__:
for k in self.__add_properties__:
setattr(self, k, feature.properties.get(k))
def __read__(self):
"""
Called by :py:attr:`.__geo_interface__`.
"""
id = None
geom = None
properties = {}
for p in class_mapper(self.__class__).iterate_properties:
if isinstance(p, ColumnProperty):
if len(p.columns) != 1: # pragma: no cover
raise NotImplementedError
col = p.columns[0]
val = getattr(self, p.key)
if col.primary_key:
id = val
elif isinstance(col.type, Geometry):
if hasattr(self, '_shape'):
geom = self._shape
elif val is not None:
geom = to_shape(val)
elif not col.foreign_keys:
properties[p.key] = val
if self.__add_properties__:
for k in self.__add_properties__:
properties[k] = getattr(self, k)
return geojson.Feature(id=id, geometry=geom, properties=properties)
@property
def __geo_interface__(self):
""" GeoInterface objects implement the Python Geo Interface, making
them candidates to serialization with the ``geojson`` module, or
the Papyrus GeoJSON renderer.
"""
return self.__read__()
Jump to Line
Something went wrong with that request. Please try again.