如何与SQLAlchemy一起正确使用association_proxy和ordering_list [英] How to properly use association_proxy and ordering_list together with SQLAlchemy
问题描述
基于SQLAlchemy Google Group上的一些帖子:
https://groups.google.com/forum/#!topic/sqlalchemy/S4_8PeRBNJw
https://groups.google.com/forum/#!topic/sqlalchemy/YRyI7ic1QkY
我假设我可以成功使用 assocation_proxy
和 ordering_list
扩展来创建两个模型之间的有序的多对多关系,如下面的Flask / SQLAlchemy代码:
from flask导入烧瓶
from flask_sqlalchemy从sqlalchemy.ext.associationproxy导入SQLAlchemy
从sqlalchemy.ext.orderinglist导入association_proxy
import ordering_list
$ b app = Flask(__ name__)
app.debug = True
app.config ['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
db = SQLAlchemy(app)
class Image(d b.Model):
__tablename__ ='images'
id = db.Column(db.Integer,primary_key = True)
filename = db.Column(db.String( 255))
class UserImage(db.Model):
__tablename__ ='user_images'
user_id = db.Column(db.Integer, db.ForeignKey('users.id'),primary_key = True)
image_id = db.Column(db.Integer,db.ForeignKey('images.id'),primary_key = True)
image = db.relationship('Image')
position = db.Column(db.Integer)
$ b $ class User(db.Model):
__tablename__ =users
id = db.Column(db.Integer,primary_key = True)
name = db.Column(db.String(255))
_images = db.relationship('UserImage',
order_by ='UserImage.position',
collection_class = ordering_list('position'))
images = association_proxy('_ images','image')
with app.app_context():
db.create_all()
use r = User(name ='Matt')
user.images.append(Image(filename ='avatar.png'))
db.session.add(user)
db.session .commit()
if __name__ =='__main__':
app.run()
但是我最终得到以下回溯:
$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ Traceback(最近的最后一次调用):
在< module>文件中的app.py,第44行。
user.images.append(Image(filename ='avatar.png'))
文件/Users/matt/.virtualenvs/sqlalchemy-temp/lib/python2.7/site-packages/sqlalchemy /ext/associationproxy.py,第595行,附加
item = self._create(value)
文件/Users/matt/.virtualenvs/sqlalchemy-temp/lib/python2.7/site (2))
返回self.creator(value)
TypeError:__init __()只需要1个参数(2给出)
/ code>
这是不可能的,还是我做了一些明显的错误?
sooo close; - )
请阅读创建新值 Option-1 :添加以下内容构造函数为 或 Option-2 :用您的函数覆盖默认的 我个人比较喜欢后者。 Based on some posts on the SQLAlchemy Google Group: https://groups.google.com/forum/#!topic/sqlalchemy/S4_8PeRBNJw
https://groups.google.com/forum/#!topic/sqlalchemy/YRyI7ic1QkY I assumed I could successfully use the But I end up with the following traceback: Is this not possible or am I doing something blatantly wrong? sooo close ;-) Please read Creation of New Values secion of Option-1: add the following constructor to or Option-2: override the default I personally favor the latter. 这篇关于如何与SQLAlchemy一起正确使用association_proxy和ordering_list的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋! association_proxy
扩展名。
为了使您的代码正常工作,您可以
UserImage
class:
$ p $ def $ __init __(self,image):
self.image = image
创建者
:
images = association_proxy('_ images','image',
creator = lambda _i:UserImage(image = _i),
)
assocation_proxy
and ordering_list
extensions to create an ordered, many to many relationship between two models such as in the following Flask/SQLAlchemy code:from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.ext.orderinglist import ordering_list
app = Flask(__name__)
app.debug = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
db = SQLAlchemy(app)
class Image(db.Model):
__tablename__ = 'images'
id = db.Column(db.Integer, primary_key=True)
filename = db.Column(db.String(255))
class UserImage(db.Model):
__tablename__ = 'user_images'
user_id = db.Column(db.Integer, db.ForeignKey('users.id'), primary_key=True)
image_id = db.Column(db.Integer, db.ForeignKey('images.id'), primary_key=True)
image = db.relationship('Image')
position = db.Column(db.Integer)
class User(db.Model):
__tablename__ = "users"
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(255))
_images = db.relationship('UserImage',
order_by='UserImage.position',
collection_class=ordering_list('position'))
images = association_proxy('_images', 'image')
with app.app_context():
db.create_all()
user = User(name='Matt')
user.images.append(Image(filename='avatar.png'))
db.session.add(user)
db.session.commit()
if __name__ == '__main__':
app.run()
$ python app.py
Traceback (most recent call last):
File "app.py", line 44, in <module>
user.images.append(Image(filename='avatar.png'))
File "/Users/matt/.virtualenvs/sqlalchemy-temp/lib/python2.7/site-packages/sqlalchemy/ext/associationproxy.py", line 595, in append
item = self._create(value)
File "/Users/matt/.virtualenvs/sqlalchemy-temp/lib/python2.7/site-packages/sqlalchemy/ext/associationproxy.py", line 522, in _create
return self.creator(value)
TypeError: __init__() takes exactly 1 argument (2 given)
association_proxy
extension.
In order to make your code work, you can eitherUserImage
class:def __init__(self, image):
self.image = image
creator
with your function:images = association_proxy('_images', 'image',
creator=lambda _i: UserImage(image=_i),
)