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from sqlalchemy import event, Column, String
from sqlalchemy.orm.session import Session
class APIMixin(object):
api_id = Column(String(255), nullable=False)
def get_api_id(self):
if self.api_id is None:
self.create_api_object()
return self.api_id
def before_created(self):
if self.api_id is None:
self.create_api_object()
def after_deleted(self):
if self.api_id is not None:
self.remove_api_object()
self.api_id = None
def create_api_object(self):
raise NotImplementedError
def remove_api_object(self):
raise NotImplementedError
def after_commit(self):
pass
class SessionHelper(object):
def __init__(self):
self.new = set()
self.dirty = set()
self.deleted = set()
event.listen(Session, 'before_flush', self.before_flush)
event.listen(Session, 'after_flush', self.after_flush)
event.listen(Session, 'after_commit', self.after_commit)
event.listen(Session, 'after_rollback', self.after_rollback)
def before_flush(self, session, flush_context, instances):
for obj in session.new:
if isinstance(obj, APIMixin):
obj.before_created()
def after_flush(self, session, flush_context):
self.new.update(
obj for obj in session.new
if isinstance(obj, APIMixin))
self.dirty.update(
obj for obj in session.dirty
if isinstance(obj, APIMixin))
self.deleted.update(
obj for obj in session.deleted
if isinstance(obj, APIMixin))
def after_commit(self, session):
for obj in self.new:
obj.after_commit()
self.new.clear()
for obj in self.dirty:
obj.after_commit()
self.dirty.clear()
for obj in self.deleted:
obj.after_deleted()
self.deleted.clear()
def after_rollback(self, session):
self.dirty.clear()
self.deleted.clear()
for obj in self.new:
obj.after_deleted()
self.new.clear()
helper = SessionHelper()
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