Heroku 内部服务器错误 500：“NoneType”对象没有“用户名”属性

Question

Trying to deploy my Flask app on Heroku when it returns the following error:

2019-11-29T09:07:28.456446+00:00 app[web.1]: File "/app/saltchat.py", line 55, in chatRoom
2019-11-29T09:07:28.456448+00:00 app[web.1]: onlineUsers.append(user.username)
2019-11-29T09:07:28.456454+00:00 app[web.1]: AttributeError: 'NoneType' object has no attribute 'username'
2019-11-29T09:07:28.458151+00:00 app[web.1]: 10.183.68.6 - - [29/Nov/2019:09:07:28 +0000] "GET /chat HTTP/1.1" 500 290 "https://salt-chat-v2.herokuapp.com/login" "Mozilla/5.0 (Windows NT 10
.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"

When I deploy the app on my local machine it works just as intended and the problem is only encountered when routing through /chat:

@app.route('/chat', methods=['POST', 'GET'])
def chatRoom():
    username = session.get('username')
    user = Users.query.filter_by(username=username).first()
    if request.referrer is None:
        return render_template('login.html')
    else:
        onlineUsers.append(user.username)
        onlineUserAvatars.append(user.avatar)
        return render_template('chat.html')

Below is the model for the database that I used:

class Users(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(32), nullable=False)
    password = db.Column(db.String, nullable=False)
    avatar = db.Column(db.Integer)

Answer 1

I think the problem is with your session user. Please modify your code as below:

@app.route('/chat', methods=['POST', 'GET'])
def chatRoom():
    username = session.get('username', '')
    try:  
        user = Users.query.filter_by(username=username).first()
    except:
        print("Something wrong")
    if request.referrer is None:
        return render_template('login.html')
    else:
        onlineUsers.append(user.username)
        onlineUserAvatars.append(user.avatar)
        return render_template('chat.html')