python – Flask和SQLalchemy NoForeignKeysError:无法确定关系User.posts上的父/子表之间的连接条件
作者:互联网
我开始使用Mega Flask教程来构建一个简单的博客风格网站.我用这个与一些python学习相关,试图加强我学到的东西.为了更多地学习,我决定将教程弃用OAuth登录文章转换为传统的登录栏.当我尝试登录时,我遇到了一个问题.
NoForeignKeysError:无法确定关系User.posts上的父/子表之间的连接条件 – 没有链接这些表的外键.确保引用列与ForeignKey或ForeignKeyConstraint相关联,或指定“primaryjoin”表达式.
由于我对Python的理解有限,我在这里遇到了一个很大的障碍.我似乎无法弄清楚我做错了什么.
这是我的models.py文件.
followers = db.Table('followers',
db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
db.Column('followed_id', db.Integer, db.ForeignKey('user.id'))
)
class User(db.Model):
__tablename__ = "users"
id = db.Column(db.Integer, primary_key=True)
nickname = db.Column(db.String(64), index=True, unique=True)
email = db.Column(db.String(120), index=True, unique=True)
password = db.Column(db.String(100))
posts = db.relationship('Post', backref='author', lazy='dynamic')
about_me = db.Column(db.String(140))
last_seen = db.Column(db.DateTime)
followed = db.relationship('User',
secondary=followers,
primaryjoin=(followers.c.follower_id == id),
secondaryjoin=(followers.c.followed_id == id),
backref=db.backref('followers', lazy='dynamic'),
lazy='dynamic')
#reviews = db.relationship('Review', backref='author', lazy='dynamic') This is the review connectino for the user.
@staticmethod
def make_unique_nickname(nickname):
if User.query.filter_by(nickname=nickname).first() is None:
return nickname
version = 2
while True:
new_nickname = nickname + str(version)
if User.query.filter_by(nickname=new_nickname).first() is None:
break
version += 1
return new_nickname
def is_authenticated(self):
return True
def is_active(self):
return True
def is_anonymous(self):
return False
def get_id(self):
try:
return unicode(self.id) #python 2
except:
return str(self.id) #python 3
def follow(self, user):
if not self.is_following(user):
self.followed.append(user)
return self
def unfollow(self, user):
if self.is_following(user):
self.followed.remove(user)
return self
def is_following(self, user):
return self.followed.filter(
followers.c.followed_id == user.id).count() > 0
def followed_posts(self):
return Post.query.join(
followers, (followers.c.followed_id == Post.user_id)).filter(
followers.c.follower_id == self.id).order_by(
Post.timestamp.desc())
def __repr__(self):
return '<User {}>'.format(self.nickname)
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
body = db.Column(db.String(140))
timestamp = db.Column(db.DateTime)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
def __repr__(self):
return '<Post {}>'.format(self.body)
这是我的views.py文件,应包含相关代码:
#This loads the user from the database
@lm.user_loader
def load_user(id):
return User.query.get(int(id))
@app.before_request
def before_request():
g.user = current_user
if g.user.is_authenticated:
g.user.last_seen = datetime.utcnow()
db.session.add(g.user)
db.session.commit()
@app.errorhandler(404)
def not_found_error(error):
return render_template('404.html'), 404
@app.errorhandler(500)
def internal_error(error):
db.session.rollback()
return render_template('500.html'), 500
@app.route('/')
@app.route('/index')
@login_required
def index():
user = g.user
posts = [ #fake array of posts
{
'author': {'nickname': 'Zach'},
'body': 'Reviewed this product!'
},
{
'author': {'nickname': 'Mark'},
'body': 'I like buttcheese!'
}
]
return render_template('index.html',
title='Home',
user=user,
posts=posts)
@app.route('/login', methods=['GET', 'POST'])
def login():
if g.user is not None and g.user.is_authenticated:
return redirect(url_for('index'))
form = LoginForm()
if form.validate_on_submit():
user = User.query.get(form.nickname.data)
session['remember_me'] = form.remember_me.data
if user:
if check_password_hash(user.password, form.password.data):
user.authenticated = True
db.session.add(user)
db.session.commit()
login_user(user, remember=True)
flash("you've been logged in!, 'success'")
return redirect(url_for('index'))
else:
flash('your email or password doesnt match!', 'error')
return render_template('login.html',
title='Sign In',
form=form)
@app.route('/logout')
def logout():
logout_user()
return redirect(url_for('index'))
我真的很挣扎,因为我还不太了解数据库关系.这是一次很棒的学习经历,但如果有人可以提供帮助,那就太棒了.
解决方法:
除了上面的帖子,我相信我已经解决了这个问题.我注意到我的tablename实际上是“用户”而不是“用户”.因此,我需要将所有外键从user.id更改为users.id,因为它正在寻找一个名为“user”的表,该表不存在.
标签:python,sqlalchemy,flask,flask-sqlalchemy,flask-login 来源: https://codeday.me/bug/20190722/1503664.html