为什么尝试使用外键创建模型实例时会收到django错误？ [英] Why do I receive a django error when trying to create a model instance with a foreign key?

问题描述

我收到以下错误：

ValueError: Cannot assign "u'ben'": "Entry.author" must be a "MyProfile" instance.

从此行：

form.author = request.session['username']

注意： Entry.author是一个外键，如下所示。

Note: Entry.author is a foreign key as seen below.

models.py

models.py

class MyProfile(models.Model):
    user = models.CharField(max_length=16)
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)

    def __unicode__(self):
        return u'%s %s %s' % (self.user, self.firstname, self.lastname)

class Entry(models.Model):
    headline= models.CharField(max_length=200,)
    body_text = models.TextField()
    author=models.ForeignKey(MyProfile, related_name='entryauthors')

    def __str__(self):
        return u'%s %s %s' % (self.headline, self.body_text, self.author)

错误说Entry.author必须是一个MyProfile实例，但是当我进入django shell并运行一个查询，我看到一个实例存在用户名ben。

The error says Entry.author must be a "MyProfile" instance, but when I go into the django shell and run a query, I see an instance exists with username ben.

<QuerySet [<MyProfile: ben ben    97201  None>]>

我现在想知道request.session ['username']是否可能没有返回正确格式的用户名我没有办法在django shell中测试（我知道的），因为我不认为你可以从shell访问请求对象。

I am now wondering if request.session['username'] is maybe not returning a correctly formatted username and I have no way to test this (that I know of) in the django shell because I don't think you can access the request object from the shell.

我的登录表单，我有这行将用户名传递给request.session。

In my login form, I have this line which is passing the username to the request.session.

if form.is_valid():
    username = form.cleaned_data['username']
    request.session['username'] = username

推荐答案

只要我使用它，外键将成为每个类中的共享对象位置（请原谅我自己的毛孔术语，授课）。

As far as i have used it, the "foreign key" is to be a shared object location in each class (please excuse the pore terminology I am self-taught).

一个示例代码如下：

class One():
    key1 = models.CharField(max_length=150)

class Two():
    key1 = models.ForeignKey(key1)

我希望这有帮助。

https://github.com/Ry10p/django-Plugis/blob/master/courses/models.py
line 52

https://github.com/Ry10p/django-Plugis/blob/master/courses/models.py line 52

-Cheers

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