如何在Python Flask中实现类似按钮的功能?

时间:2018-10-05 12:31:36

标签: python flask sqlalchemy flask-sqlalchemy

因此,我试图向我的代码中添加一个喜欢按钮的功能,该功能允许用户喜欢特定帖子。点赞次数将链接到已登录的用户,并显示点赞次数。实施前端并不困难,但是后端存在问题。

我是using this post here as a guide which does a follower system instead

这是我到目前为止所拥有的?

我在models.py中为喜欢创建了一个表:

likers = db.Table('likers',
    db.Column('liker_id', db.Integer, db.ForeignKey('post.id')),
    db.Column('liked_id', db.Integer, db.ForeignKey('post.id'))
)

在我的用户类的Models.py中:

class User(db.Model, UserMixin):
#Code 
liked = db.relationship(
    'User', secondary=likers,
    primaryjoin=(likers.c.liker_id == id),
    secondaryjoin=(likers.c.liked_id == id),
    backref = db.backref('likers', lazy='dynamic'), lazy='dynamic')
def like(self, post):
    if not self.is_liking(post):
        self.liked.append(post)

def unlike(self, post):
    if self.is_liking(post):
        self.liked.remove(post)

def is_liking(self, post):
    return self.liked.filter(
        likers.c.liked_id == post.id).count() > 0

在routes.py中-对于我的用户蓝图,我有:

@users.route("/like/<int:post_id>")
@login_required
def like(post_id):
 post = Post.query.get_or_404(post_id)
 current_user.like(post)
 db.session.commit()
 flash('Post has been liked')
 return redirect(url_for('posts.post', post_id=post.id))

@users.route("/unlike/<int:post_id>")
@login_required
def unlike(post_id):
 post = Post.query.get_or_404(post_id)
 current_user.unlike(post)
 db.session.commit()
 flash('Post has been unliked')
 return redirect(url_for('posts.post', post_id=post.id))    

我在做什么错?我不断收到诸如以下错误:

builtins.KeyError
KeyError: 'likers'

我已经完成了一个评论部分,并且我知道喜欢的人的关系将类似于评论,但是我正在努力实现它。我对Flask还是比较陌生,我曾尝试使用这些文档,但找不到任何可帮助我的东西...

这是我最后的希望。

3 个答案:

答案 0 :(得分:2)

class User(UserMixin, db.Model):
    # Code
    liked = db.relationship(
        'PostLike',
        foreign_keys='PostLike.user_id',
        backref='user', lazy='dynamic')

    def like_post(self, post):
        if not self.has_liked_post(post):
            like = PostLike(user_id=self.id, post_id=post.id)
            db.session.add(like)

    def unlike_post(self, post):
        if self.has_liked_post(post):
            PostLike.query.filter_by(
                user_id=self.id,
                post_id=post.id).delete()

    def has_liked_post(self, post):
        return PostLike.query.filter(
            PostLike.user_id == self.id,
            PostLike.post_id == post.id).count() > 0


class PostLike(db.Model):
    __tablename__ = 'post_like'
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    post_id = db.Column(db.Integer, db.ForeignKey('post.id'))


@app.route('/like/<int:post_id>/<action>')
@login_required
def like_action(post_id, action):
    post = Post.query.filter_by(id=post_id).first_or_404()
    if action == 'like':
        current_user.like_post(post)
        db.session.commit()
    if action == 'unlike':
        current_user.unlike_post(post)
        db.session.commit()
    return redirect(request.referrer)

然后,当您列出自己的帖子时,设置锚点如下:

{% for post in posts %}
  {% if current_user.has_liked_post(post) %}
    <a href="{{ url_for('like_action', post_id=post.id, action='unlike') }}">Unlike</a>
  {% else %}
    <a href="{{ url_for('like_action', post_id=post.id, action='like') }}">Like</a>
  {% endif %}
{% endfor %}

假设您的Post模型看起来像这样:

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    body = db.Column(db.Text)
    author_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    recipient_id = db.Column(db.Integer, db.ForeignKey('user.id'))

    likes = db.relationship('PostLike', backref='post', lazy='dynamic')

您将使用:

p = Post.query.filter_by(id=1).first()
p.likes.count()

或者,您可以在.html文件中使用它:

{% for post in posts %}
  {% if current_user.has_liked_post(post) %}
    <a href="{{ url_for('like_action', post_id=post.id, action='unlike') }}">Unlike</a>
  {% else %}
    <a href="{{ url_for('like_action', post_id=post.id, action='like') }}">Like</a>
  {% endif %}
  {{ post.likes.count() }} likes
{% endfor %}

答案 1 :(得分:0)

您的错误表明用户实例没有正确定义的likers关系。

我怀疑这里有几个错误:

  1. 您的likers表应该具有指向liker_id的外键,指向用户表,而不是帖子。
  2. 您在liked模型中的User关系应该是与Post模型(以likers表为辅助关系)的关系,而不是与自身的关系(即User模型)。 尝试以下这种关系:

    liked = db.relationship(
    'Post', secondary="likers",
    primaryjoin="likers.liker_id == users.id",
    secondaryjoin="likers.liked_id == posts.id",
    backref=db.backref('likers', lazy='dynamic'), lazy='dynamic')
    
  3. 您的is_liking()方法似乎很奇怪。我会这样写:

    (如果不希望每个用户收到很多喜欢的帖子)return post in self.liked

    (如果期望每个用户有很多喜欢的帖子)return db.session.execute("SELECT COUNT(*) FROM likers WHERE liked_id = :post_id AND liker_id = :user_id", {'user_id': self.id, 'post_id': post.id}).fetchone()[0] > 0

  4. (无关,可能不正确),您的User模型从db.ModelUserMixin继承的顺序很重要,当前,您的UserMixin仅用于db.Model中找不到的方法。并且不会覆盖任何内容(也许就是您想要的)。参考:Python的Method Resolution Order(MRO)

答案 2 :(得分:0)

以上代码有效,但是由于“ current_user”而注销了用户制造商错误。所以我们的html文件必须是这样的

{% for post in posts %}
    {% if current_user.is_authenticated %}
        {% if current_user.has_liked_post(post) %}
            <a href="{{ url_for('like_action', post_id=post.id, action='unlike') }}">Unlike</a>
        {% else %}
            <a href="{{ url_for('like_action', post_id=post.id, action='like') }}">Like</a>
        {% endif %}
        {{ post.likes.count() }} likes
    {% else %}
        {{ post.likes.count() }} likes
    {% endif %}{% endfor %}