lazy loaded objects

parse_rest/datatypes.py

@@ -20,10 +20,19 @@ from parse_rest.connection import API_ROOT, ParseBase
 from parse_rest.query import QueryManager
 
 
+def complex_type(name=None):
+    '''Decorator for registering complex types'''
+    def wrapped(cls):
+        ParseType.type_mapping[name or cls.__name__] = cls
+        return cls
+    return wrapped
+
+
 class ParseType(object):
+    type_mapping = {}
 
     @staticmethod
-    def convert_from_parse(parse_data, class_name):
+    def convert_from_parse(parse_data):
 
         is_parse_type = isinstance(parse_data, dict) and '__type' in parse_data
 
@@ -31,28 +40,8 @@ class ParseType(object):
         if not is_parse_type:
             return parse_data
 
-        # determine just which kind of parse type this element is - ie: a built in parse type such as File, Pointer, User etc
-        parse_type = parse_data['__type']
-
-        # if its a pointer, we need to handle to ensure that we don't mishandle a circular reference
-        if parse_type == "Pointer":
-            # grab the pointer object here
-            return Pointer.from_native(class_name, **parse_data)
-
-        # embedded object by select_related
-        if parse_type == "Object":
-            return EmbeddedObject.from_native(class_name, **parse_data)
-
-        # now handle the other parse types accordingly
-        native = {
-            'Date': Date,
-            'Bytes': Binary,
-            'GeoPoint': GeoPoint,
-            'File': File,
-            'Relation': Relation
-            }.get(parse_type)
-
-        return native and native.from_native(**parse_data) or parse_data
+        native = ParseType.type_mapping.get(parse_data['__type'])
+        return  native.from_native(**parse_data) if native else parse_data
 
     @staticmethod
     def convert_to_parse(python_object, as_pointer=False):
@@ -69,7 +58,7 @@ class ParseType(object):
         transformation_map = {
             datetime.datetime: Date,
             Object: Pointer
-            }
+        }
 
         if python_type in transformation_map:
             klass = transformation_map.get(python_type)
@@ -85,36 +74,18 @@ class ParseType(object):
         return cls(**kw)
 
     def _to_native(self):
-        return self._value
+        raise NotImplementedError("_to_native must be overridden")
 
 
+@complex_type('Pointer')
 class Pointer(ParseType):
 
     @classmethod
-    def _prevent_circular(cls, parent_class_name, objectData):
-        # TODO this should be replaced with more clever checking, instead of simple class mathching original id should be compared
-        # also circular refs through more object are now ignored, in fact lazy loaded references will be best solution
-        objectData = dict(objectData)
-        # now lets see if we have any references to the parent class here
-        for key, value in six.iteritems(objectData):
-            if isinstance(value, dict) and "className" in value and value["className"] == parent_class_name:
-                # simply put the reference here as a string  -- not sure what the drawbacks are for this but it works for me
-                objectData[key] = value["objectId"]
-        return objectData
-
-    @classmethod
-    def from_native(cls, parent_class_name=None, **kw):
-        # grab the object data manually here so we can manipulate it before passing back an actual object
+    def from_native(cls, **kw):
+        # create object with only objectId and unloaded flag. it is automatically loaded when any other field is accessed
         klass = Object.factory(kw.get('className'))
-        objectData = klass.GET("/" + kw.get('objectId'))
-
-        # now lets check if we have circular references here
-        if parent_class_name:
-            objectData = cls._prevent_circular(parent_class_name, objectData)
+        return klass(objectId=kw.get('objectId'), _is_loaded=False)
 
-        # set a temporary flag that will remove the recursive pointer types etc
-        klass = Object.factory(kw.get('className'))
-        return klass(**objectData)
 
     def __init__(self, obj):
         self._object = obj
@@ -124,24 +95,25 @@ class Pointer(ParseType):
             '__type': 'Pointer',
             'className': self._object.__class__.__name__,
             'objectId': self._object.objectId
-            }
+        }
 
 
+@complex_type('Object')
 class EmbeddedObject(ParseType):
     @classmethod
-    def from_native(cls, parent_class_name=None, **kw):
-        if parent_class_name:
-            kw = Pointer._prevent_circular(parent_class_name, kw)
+    def from_native(cls, **kw):
         klass = Object.factory(kw.get('className'))
         return klass(**kw)
 
 
+@complex_type()
 class Relation(ParseType):
     @classmethod
     def from_native(cls, **kw):
         pass
 
 
+@complex_type()
 class Date(ParseType):
     FORMAT = '%Y-%m-%dT%H:%M:%S.%f%Z'
 
@@ -167,6 +139,7 @@ class Date(ParseType):
             }
 
 
+@complex_type('Bytes')
 class Binary(ParseType):
 
     @classmethod
@@ -181,6 +154,7 @@ class Binary(ParseType):
         return {'__type': 'Bytes', 'base64': self._encoded}
 
 
+@complex_type()
 class GeoPoint(ParseType):
 
     @classmethod
@@ -199,6 +173,7 @@ class GeoPoint(ParseType):
             }
 
 
+@complex_type()
 class File(ParseType):
 
     @classmethod
@@ -233,14 +208,10 @@ class Function(ParseBase):
         return self.POST('/' + self.name, **kwargs)
 
 
-class ParseResource(ParseBase, Pointer):
+class ParseResource(ParseBase):
 
     PROTECTED_ATTRIBUTES = ['objectId', 'createdAt', 'updatedAt']
 
-    @classmethod
-    def retrieve(cls, resource_id):
-        return cls(**cls.GET('/' + resource_id))
-
     @property
     def _editable_attrs(self):
         protected_attrs = self.__class__.PROTECTED_ATTRIBUTES
@@ -248,19 +219,23 @@ class ParseResource(ParseBase, Pointer):
         return dict([(k, v) for k, v in self.__dict__.items() if allowed(k)])
 
     def __init__(self, **kw):
-        for key, value in kw.items():
-            setattr(self, key, ParseType.convert_from_parse(value, self.__class__.__name__))
+        self.objectId = None
+        self._init_attrs(kw)
+
+    def __getattr__(self, attr):
+        # if object is not loaded and attribute is missing, try to load it
+        if not self.__dict__.get('_is_loaded', True):
+            del self._is_loaded
+            self._init_attrs(self.GET(self._absolute_url))
+        return object.__getattribute__(self, attr) #preserve default if attr not exists
+
+    def _init_attrs(self, args):
+        for key, value in six.iteritems(args):
+            setattr(self, key, ParseType.convert_from_parse(value))
 
     def _to_native(self):
         return ParseType.convert_to_parse(self)
 
-    def _get_object_id(self):
-        return self.__dict__.get('_object_id')
-
-    def _set_object_id(self, value):
-        if '_object_id' in self.__dict__:
-            raise ValueError('Can not re-set object id')
-        self._object_id = value
 
     def _get_updated_datetime(self):
         return self.__dict__.get('_updated_at') and self._updated_at._date
@@ -294,8 +269,7 @@ class ParseResource(ParseBase, Pointer):
             call_back(response)
 
     def _update(self, batch=False):
-        response = self.__class__.PUT(self._absolute_url, batch=batch,
-                                      **self._to_native())
+        response = self.__class__.PUT(self._absolute_url, batch=batch, **self._to_native())
 
         def call_back(response_dict):
             self.updatedAt = response_dict['updatedAt']
@@ -307,19 +281,12 @@ class ParseResource(ParseBase, Pointer):
 
     def delete(self, batch=False):
         response = self.__class__.DELETE(self._absolute_url, batch=batch)
-        def call_back(response_dict):
-            self.__dict__ = {}
-
         if batch:
-            return response, call_back
-        else:
-            call_back(response)
+            return response, lambda response_dict: None
+
 
-    _absolute_url = property(
-        lambda self: '/'.join([self.__class__.ENDPOINT_ROOT, self.objectId])
-        )
+    _absolute_url = property(lambda self: '/'.join([self.__class__.ENDPOINT_ROOT, self.objectId]))
 
-    objectId = property(_get_object_id, _set_object_id)
     createdAt = property(_get_created_datetime, _set_created_datetime)
     updatedAt = property(_get_updated_datetime, _set_updated_datetime)
 
@@ -365,10 +332,7 @@ class Object(six.with_metaclass(ObjectMetaclass, ParseResource)):
 
     @property
     def as_pointer(self):
-        return Pointer(**{
-                'className': self.__class__.__name__,
-                'objectId': self.objectId
-                })
+        return Pointer(self)
 
     def increment(self, key, amount=1):
         """

parse_rest/user.py

@@ -46,7 +46,7 @@ class User(ParseResource):
         if password is not None:
             self = User.login(self.username, password)
 
-        user = User.retrieve(self.objectId)
+        user = User.Query.get(objectId=self.objectId)
         if user.objectId == self.objectId and user.sessionToken == session_token:
             self.sessionToken = session_token