Difficulté à sérialiser le type de colonne Géographie avec sqlalchemy marshmallow

Question

Je tente d'utiliser Marshmallow pour désérialiser et sérialiser des objets SQLAlchemy, mais je rencontre un problème lorsque je traite des champs de géographie dans l'ORM.

Tout d'abord le modèle:

class Address(db.Model, TableColumnsBase): 
    __tablename__ = 'address' 
    addressLine1 = db.Column(String(255), nullable=True, info="Street address, company name, c/o") 
    addressLine2 = db.Column(String(255), nullable=True, info="Apartment, suite, unit, building floor, etc") 
    countryCode = db.Column(String(255), nullable=True, info="Country code such as AU, US etc") 
    suburb = db.Column(String(255), nullable=True, info="Users suburb such as Elizabeth Bay") 
    postcode = db.Column(String(32), nullable=True, info="Users postcode such as 2011 for Elizabeth Bay") 
    state = db.Column(String(64), info="State for user such as NSW") 
    user_presence = one_to_many('UserPresence', backref = 'user', lazy='select', cascade='all, delete-orphan') 

    location = Column(Geography(geometry_type='POINT', srid=4326)) 
    discriminator = Column('type', String(50)) 
    __mapper_args__ = {'polymorphic_on': discriminator} 

    def as_physical(self): 
     pa = { # TODO - stub, make it proper 
      "latitude": 2.1, 
      "longitude": 1.1, 
      "unitNumber": '1', 
      "streetNumber": self.addressLine1, 
      "streetName": self.addressLine2, 
      "streetType": 'street', 
      "suburb": self.suburb, 
      "postcode": self.postcode 
     } 
     return pa 

Deuxièmement, le schéma de guimauve:

class AddressSchema(ModelSchema): 
    class Meta: 
     model = Address 
     sqla_session 

l'erreur en essayant de courir:

/Users/james/.virtualenvs/trustmile-api-p2710/bin/python /Users/james/Documents/workspace/trustmile-backend/trustmile/tests/postgis_scratch.py 
Traceback (most recent call last): 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/tests/postgis_scratch.py", line 1, in <module> 
    from app import db 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/__init__.py", line 54, in <module> 
    from app.api.consumer_v1 import bp as blueprint 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/api/__init__.py", line 4, in <module> 
    import courier_v1 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/api/courier_v1/__init__.py", line 5, in <module> 
    from .routes import routes 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/api/courier_v1/routes.py", line 10, in <module> 
    from .api.nearestNeighbours_latitude_longitude import NearestneighboursLatitudeLongitude 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/api/courier_v1/api/__init__.py", line 5, in <module> 
    from app.ops import requesthandler 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/ops/requesthandler.py", line 1, in <module> 
    from app.ops.consumer_operations import cons_ops, ConsumerOperationsFactory 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/ops/consumer_operations.py", line 19, in <module> 
    from app.users.serialize import ApplicationInstallationSchema, UserAddressSchema, ConsumerUserSchema, CourierUserSchema 
    File "/Users/james/Documents/workspace/trustmile-backend/trustmile/app/users/serialize.py", line 40, in <module> 
    class AddressSchema(ModelSchema): 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow/schema.py", line 116, in __new__ 
    dict_cls=dict_cls 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/schema.py", line 57, in get_declared_fields 
    declared_fields = mcs.get_fields(converter, opts) 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/schema.py", line 90, in get_fields 
    include_fk=opts.include_fk, 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/convert.py", line 77, in fields_for_model 
    field = self.property2field(prop) 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/convert.py", line 95, in property2field 
    field_class = self._get_field_class_for_property(prop) 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/convert.py", line 153, in _get_field_class_for_property 
    field_cls = self._get_field_class_for_column(column) 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/convert.py", line 123, in _get_field_class_for_column 
    return self._get_field_class_for_data_type(column.type) 
    File "/Users/james/.virtualenvs/trustmile-api-p2710/lib/python2.7/site-packages/marshmallow_sqlalchemy/convert.py", line 145, in _get_field_class_for_data_type 
    'Could not find field column of type {0}.'.format(types[0])) 
marshmallow_sqlalchemy.exceptions.ModelConversionError: Could not find field column of type <class 'geoalchemy2.types.Geography'>. 

J'ai essayé quelques remplacements sur le champ de localisation cependant en vain. Toute aide très appréciée.

Mise à jour le 24 janvier 2016

Ceci est mon code tel qu'il se présente comme le moment avec un modèle plus simple:

Le SQLAlchemyModel:

class Location(db.Model, TableColumnsBase): 
    __tablename__ = "location" 
    loc = db.Column(Geography(geometry_type='POINT', srid=4326)) 

L'objet de schéma marshmallow_sqlalchemy

class LocationSchema(ModelSchema): 
    loc = GeographySerializationField(attribute='loc') 
    class Meta: 
     model = Location 
     sqla_session = db.session 
     model_converter = GeoConverter 

Autres plomberie par suggestions:

class GeoConverter(ModelConverter): 
    SQLA_TYPE_MAPPING = ModelConverter.SQLA_TYPE_MAPPING.copy() 
    SQLA_TYPE_MAPPING.update({ 
     Geography: fields.Str 
    }) 


class GeographySerializationField(fields.Field): 
    def _serialize(self, value, attr, obj): 
     if value is None: 
      return value 
     else: 
      if isinstance(value, Geography): 
       return json.dumps({'latitude': db.session.scalar(geo_funcs.ST_X(value)), 'longitude': db.session.scalar(geo_funcs.ST_Y(value))}) 
      else: 
       return None 

    def _deserialize(self, value, attr, data): 
     """Deserialize value. Concrete :class:`Field` classes should implement this method. 

     :param value: The value to be deserialized. 
     :param str attr: The attribute/key in `data` to be deserialized. 
     :param dict data: The raw input data passed to the `Schema.load`. 
     :raise ValidationError: In case of formatting or validation failure. 
     :return: The deserialized value. 

     .. versionchanged:: 2.0.0 
      Added ``attr`` and ``data`` parameters. 
     """ 
     if value is None: 
      return value 
     else: 
      if isinstance(value, Geography): 
       return {'latitude': db.session.scalar(geo_funcs.ST_X(value)), 'longitude': db.session.scalar(geo_funcs.ST_Y(value))} 
      else: 
       return None 

En exécutant le code:

from app.users.serialize import * 
from app.model.meta.schema import Location 
l = LocationSchema() 
loc = Location(27.685994, 85.317815) 
r = l.load(loc) 
print r 

Le résultat que je reçois est:

UnmarshalResult(data={}, errors={u'_schema': [u'Invalid input type.']}) 

Answer 1

résolu le problème, d'une part abusait les méthodes, mais voici la réponse:

Pour sérialisation:

class GeoConverter(ModelConverter): 
    SQLA_TYPE_MAPPING = ModelConverter.SQLA_TYPE_MAPPING.copy() 
    SQLA_TYPE_MAPPING.update({ 
     Geography: fields.Str 
    }) 



class GeographySerializationField(fields.String): 
    def _serialize(self, value, attr, obj): 
     if value is None: 
      return value 
     else: 
      if attr == 'loc': 
       return {'latitude': db.session.scalar(geo_funcs.ST_X(value)), 'longitude': db.session.scalar(geo_funcs.ST_Y(value))} 
      else: 
       return None 

    def _deserialize(self, value, attr, data): 
     """Deserialize value. Concrete :class:`Field` classes should implement this method. 

     :param value: The value to be deserialized. 
     :param str attr: The attribute/key in `data` to be deserialized. 
     :param dict data: The raw input data passed to the `Schema.load`. 
     :raise ValidationError: In case of formatting or validation failure. 
     :return: The deserialized value. 

     .. versionchanged:: 2.0.0 
      Added ``attr`` and ``data`` parameters. 
     """ 
     if value is None: 
      return value 
     else: 
      if attr == 'loc': 
       return WKTGeographyElement('POINT({0} {1})'.format(str(value.get('longitude')), str(value.get('latitude')))) 
      else: 
       return None 

La définition du schéma:

class LocationSchema(ModelSchema): 
    loc = GeographySerializationField(attribute='loc') 
    id = fields.UUID(Location, attribute='id') 
    class Meta: 
     model = Location 
     sqla_session = db.session 
     model_converter = GeoConverter 

Et le test:

from app.users.serialize import * 
from app.model.meta.schema import Location 
from app import db 
l = LocationSchema() 
loc = Location(27.685994, 85.317815) 
db.session.add(loc) 
db.session.commit() 
r = l.dump(loc).data 

print r 

loc_obj = l.load(r) 

print loc_obj.data 

Answer 2

Vous pouvez remplacer la classe ModelConverter et spécifier un mappage personnalisé pour votre champ de géographie. Voir la réponse de Jair Perrut ici How to use marshmallow to serialize a custom sqlalchemy field?

from marshmallow_sqlalchemy import ModelConverter 
from marshmallow import fields 

class GeoConverter(ModelConverter): 
    SQLA_TYPE_MAPPING = ModelConverter.SQLA_TYPE_MAPPING.copy() 
    SQLA_TYPE_MAPPING.update({ 
     Geography: fields.Str 
    }) 

class Meta: 
    model = Address 
    sqla_session = session 
    model_converter = GeoConverter