python - Flask和SQLalchemy NoForeignKeysError : Could not determine join condition between parent/child tables on relationship User.帖子

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我从Mega Flask教程开始，建立了一个简单的博客风格的网站。我将它与一些python研究结合起来使用，以尝试加强我所学到的知识。为了进一步学习，我决定将教程已弃用的OAuth登录替换为传统的 flask 登录。我尝试登录时遇到问题。

NoForeignKeysError:无法确定关系User.posts的父/子表之间的联接条件-没有链接这些表的外键。确保引用列与ForeignKey或ForeignKeyConstraint关联，或指定“primaryjoin”表达式。

由于对Python的了解有限，我在这里遇到了很大的障碍。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，其中应包含相关代码:

#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'))

我真的为此感到挣扎，因为我对数据库的关系还不够了解。这是一次很棒的学习经历，但是如果有人可以提供帮助，那就太好了。

最佳答案

除了上面的帖子，我相信我已经解决了这个问题。我注意到我的表名实际上是“用户”，而不是“用户”。结果，我需要将所有外键从user.id更改为users.id，因为它正在寻找不存在的名为“user”的表。

关于python - Flask和SQLalchemy NoForeignKeysError : Could not determine join condition between parent/child tables on relationship User.帖子，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/34234964/