Flask SQLAlchemy 'str' 对象没有属性 '_sa_instance_state'

Question

我正在尝试使用 SQLAlchemy + Flask 将项目添加到我的数据库中，但不断收到错误消息。

class users(db.Model):
    userid = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80))
    email = db.Column(db.String(120))
    password = db.Column(db.String(80))
    duguns = db.relationship('dugun', backref='whuser', lazy='dynamic')
    yorums = db.relationship('yorum', backref='whuser', lazy='dynamic')
    genels = db.relationship('genel', backref='whuser', lazy='dynamic')
    bilgis = db.relationship('bilgi', backref='whuser', lazy='dynamic')

class bilgi(db.Model):
    kisiselid = db.Column(db.Integer, primary_key=True)
    userid = db.Column(db.Integer, db.ForeignKey('users.userid'))
    gelinAdi = db.Column(db.String(80))
    damatAdi = db.Column(db.String(80))
    gelinFoto = db.Column(db.String(80))
    damatFoto = db.Column(db.String(80))
    gelinBio = db.Column(db.String(120))
    damatBio = db.Column(db.String(80))



@app.route("/admin", methods=["GET","POST"])
@login_required
def admin():
    form = KisiForm(request.form)
    if request.method == "POST":
        gelinAdi = form.gelinAdi.data
        gelinFoto = form.gelinFoto.data
        gelinBio = form.gelinBio.data
        damatAdi = form.damatAdi.data
        damatFoto = form.damatFoto.data
        damatBio = form.damatBio.data
        whuser = session["username"]

        kisi = bilgi(whuser = whuser, gelinAdi = gelinAdi, gelinFoto = gelinFoto, gelinBio = gelinBio, damatAdi = damatAdi, damatFoto = damatFoto, damatBio = damatBio)
        db.session.add(kisi)
        db.session.commit()
        return redirect(url_for("admin"))

    return render_template("admin/index.html",form=form)

这就是代码。当我运行 Python 文件时，出现此错误：

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
    raise value
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/bozkurt/Desktop/davetiye/site.py", line 70, in decorated_function
    return f(*args, **kwargs)
  File "/Users/bozkurt/Desktop/davetiye/site.py", line 172, in admin
    kisi = bilgi(whuser = whuser, gelinAdi = gelinAdi, gelinFoto = gelinFoto, gelinBio = gelinBio, damatAdi = damatAdi, damatFoto = damatFoto, damatBio = damatBio)
  File "<string>", line 4, in __init__

  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/state.py", line 417, in _initialize_instance
    manager.dispatch.init_failure(self, args, kwargs)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 249, in reraise
    raise value
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/state.py", line 414, in _initialize_instance
    return manager.original_init(*mixed[1:], **kwargs)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/ext/declarative/base.py", line 700, in _declarative_constructor
    setattr(self, k, kwargs[k])
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 229, in __set__
    instance_dict(instance), value, None)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 813, in set
    value = self.fire_replace_event(state, dict_, value, old, initiator)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 833, in fire_replace_event
    state, value, previous, initiator or self._replace_token)
  File "/usr/local/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 1181, in emit_backref_from_scalar_set_event
    child_state, child_dict = instance_state(child),\
AttributeError: 'str' object has no attribute '_sa_instance_state'

AttributeError: 'str' object has no attribute '_sa_instance_state。我该怎么办？

Answer 1

您将列定义为反向引用：

bilgis = db.relationship('bilgi', backref='whuser', lazy='dynamic')

表示值they're set to represents an ORM object - 不是单个字符串。但是，您在创建对象时只发送字符串（用户名）：

whuser = session["username"]
kisi = bilgi(whuser = whuser, ...)

确保提供从 ORM 返回的用户对象：

bilig(whuser=<actual user object from the ORM>, ..)

您可以通过首先从 ORM 中获取用户来做到这一点：

user = users.query.filter_by(username=whuser).first()

然后在创建依赖对象时使用该值：

bilig(whuser=user, ..)