Add a framework for generic views
This commit does not enable the new code, as such there
should be no change in functionality. In order to use the
new code the maps.py file should be updated to point at the
new views/models/sponsor.py module.
Patch by: Sverre Rabbelier
Reviewed by: to-be-reviewed
#!/usr/bin/python2.5
#
# Copyright 2008 the Melange authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Helpers functions for updating different kinds of models in datastore.
"""
__authors__ = [
'"Todd Larsen" <tlarsen@google.com>',
'"Sverre Rabbelier" <sverer@rabbelier.nl>',
'"Pawel Solyga" <pawel.solyga@gmail.com>',
]
from google.appengine.ext import db
from soc.logic import key_name
from soc.logic import out_of_band
class Logic():
"""Base logic for entity classes.
The BaseLogic class functions specific to Entity classes by relying
on the the child-classes to implement _model, _name and _key_name
"""
def _updateField(self, model, name, value):
"""Hook called when a field is updated.
Base classes should override if any special actions need to be
taken when a field is updated. The field is not updated if the
method does not return a True value.
"""
return True
def getFromKeyName(self, key_name):
""""Returns User entity for key_name or None if not found.
-
- Args:
- key_name: key name of entity
"""
return self._model.get_by_key_name(key_name)
def getFromFields(self, **kwargs):
"""Returns the entity for a given link name, or None if not found.
Args:
**kwargs: the fields of the entity that uniquely identifies it
"""
key_name = self.getKeyNameForFields(**kwargs)
if key_name:
entity = self._model.get_by_key_name(key_name)
else:
entity = None
return entity
def getIfFields(self, **kwargs):
"""Returns entity for supplied link name if one exists.
Args:
**kwargs: the fields of the entity that uniquely identifies it
Returns:
* None if a field is false.
* Entity for supplied fields
Raises:
out_of_band.ErrorResponse if link name is not false, but no entity
with the supplied link name exists in the Datastore
"""
if not all(kwargs.values()):
# exit without error, to let view know that link_name was not supplied
return None
entity = self.getFromFields(**kwargs)
if entity:
# an entity exist for this link_name, so return that entity
return entity
fields = []
for key, value in kwargs.iteritems():
fields.extend('"%s" is "%s" ' % (key, value))
# else: fields were supplied, but there is no Entity that has it
raise out_of_band.ErrorResponse(
'There is no %s with %s.' % (self._name, ''.join(fields)), status=404)
def getKeyNameForFields(self, **kwargs):
"""Return a Datastore key_name for a Entity from the specified fields.
Args:
**kwargs: the fields of the entity that uniquely identifies it
"""
if not all(kwargs.values()):
return None
return self._keyName(**kwargs)
def extractKeyFields(self, fields):
"""Extracts all the fields from that are in the mode's key_fields property
Args:
fields: A dict from which the fields should be extracted
"""
key_fields = {}
keys = fields.keys()
for key in keys[:]:
if key in self._model.key_fields:
key_fields[key] = fields[key]
return key_fields
def getForLimitAndOffset(self, limit, offset=0):
"""Returns entities for given offset and limit or None if not found.
Args:
limit: max amount of entities to return
offset: optional offset in entities list which defines first entity to
return; default is zero (first entity)
"""
query = self._model.all()
return query.fetch(limit, offset)
def updateModelProperties(self, model, **model_properties):
"""Update existing model entity using supplied model properties.
Args:
model: a model entity
**model_properties: keyword arguments that correspond to model entity
properties and their values
Returns:
the original model entity with any supplied properties changed
"""
def update():
return self._unsafeUpdateModelProperties(model, **model_properties)
return db.run_in_transaction(update)
def _unsafeUpdateModelProperties(self, model, **model_properties):
"""(see updateModelProperties)
Like updateModelProperties(), but not run within a transaction.
"""
properties = model.properties()
for prop in properties.values():
name = prop.name
if not name in self._skip_properties and name in model_properties:
value = model_properties[prop.name]
if self._updateField(model, name, value):
prop.__set__(model, value)
model.put()
return model
def updateOrCreateFromKeyName(self, properties, key_name):
"""Update existing entity, or create new one with supplied properties.
Args:
properties: dict with entity properties and their values
key_name: the key_name of the entity that uniquely identifies it
Returns:
the entity corresponding to the key_name, with any supplied
properties changed, or a new entity now associated with the
supplied key_name and properties.
"""
entity = self.getFromKeyName(key_name)
if not entity:
# entity did not exist, so create one in a transaction
entity = self._model.get_or_insert(key_name, **properties)
# there is no way to be sure if get_or_insert() returned a new entity or
# got an existing one due to a race, so update with properties anyway,
# in a transaction
return self.updateModelProperties(entity, **properties)
def updateOrCreateFromFields(self, properties, **kwargs):
"""Like updateOrCreateFromKeyName, but resolves **kwargs to a key_name first
"""
# attempt to retrieve the existing entity
key_name = self.getKeyNameForFields(**kwargs)
return self.updateOrCreateFromKeyName(properties, key_name)
def isDeletable(self, entity):
"""Returns whether the specified entity can be deleted
"""
# TODO(pawel.solyga): Create specific delete method for Sponsor model
# Check if Sponsor can be deleted (has no Hosts and Programs)
return True
def delete(self, entity):
"""Delete existing entity from datastore.
Args:
entity: an existing entity in datastore
"""
entity.delete()