我在将Model.objects.get与自定义模型一起使用时遇到问题，该模型包含标准Django用户作为其中一个字段。以下是基本属性：
class Student(models.Model):
user = models.ForeignKey(User, unique=True)
school = models.ForeignKey(School)
isHead = models.BooleanField()
我制作了一个新的School，User和Student，并毫无问题地保存了所有内容。所以我将以下内容输入manage.py shell，其中new是User对象的变量：
Student.objects.get(user = new)
然后，我收到错误：
ValueError: Cannot assign "5312840185413632L": "Student.user" must be a "User" instance.
我做了一些研究，我理解上面的意思是说我传递了一些不一个User对象作为参数。但是，我已经定义了
new = User(username="new user")
所以我无法弄清楚我做错了什么。
非常感谢任何帮助。如果它有帮助，我在Eclipse中工作，这对我来说是新的，虽然Django / python不是。
编辑：这是我的自定义类的完整代码：
class School(models.Model):
def level(self):
return get_max_triangle_num_less_than(self.rep / SCHOOL_REP_LEVEL_MODIFIER)
name = models.CharField(max_length=64)
# Rep could also be a DecimalField (needs max_digits and decimal_places specified)
rep = models.IntegerField(default = 0)
num_students = models.IntegerField(default = 0)
def __init__(self, name, *args, **kwargs):
models.Model.__init__(self, *args, **kwargs)
self.name = name
def __str__(self, *args, **kwargs):
return self.name + ", " + str(self.num_students) + " students"
class Student(models.Model):
def level(self):
return get_max_triangle_num_less_than(self.rep / STUDENT_REP_LEVEL_MODIFIER)
user = models.ForeignKey(User, unique=True)
school = models.ForeignKey(School)
isHead = models.BooleanField()
referral_code = models.CharField(max_length=128, unique=True)
referred_by = models.ForeignKey(User, blank=True, null=True)
rep = models.IntegerField(default = 0)
def __init__(self, user, school, referred_by = None, *args, **kwargs):
models.Model.__init__(self, *args, **kwargs)
self.user = user
self.school = school
if referred_by:
self.referred_by = referred_by
# This automatically creates a custom string of letters/numbers -- I thought it was
# the easiest way to make a custom "referral code" which can be used to link a
# registration to the referrer
self.referral_code = str(uuid.uuid4())
self.school.num_students += 1
def __str__(self):
something = str(self.user.username)
if self.isHead:
something += ", Head at "
else:
something += ", at "
something += self.school.name + ", " + str(self.rep) + " rep points"
return something
以下是我在shell + traceback中输入的内容：
>>> from spudmart.campusrep.models import User, School, Student
>>> usr = User(username="user")
>>> usr.save()
>>> sch = School(name = "school")
>>> sch.save()
>>> stu = Student(user = usr, school = sch)
>>> stu.save()
>>> Student.objects.get(user = usr)
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/Users/Lucy/Code/Git/spudder/spudmart/src/django/db/models/manager.py", line 132, in get
return self.get_query_set().get(*args, **kwargs)
File "/Users/Lucy/Code/Git/spudder/spudmart/src/django/db/models/query.py", line 346, in get
num = len(clone)
File "/Users/Lucy/Code/Git/spudder/spudmart/src/django/db/models/query.py", line 82, in __len__
self._result_cache = list(self.iterator())
File "/Users/Lucy/Code/Git/spudder/spudmart/src/django/db/models/query.py", line 288, in iterator
obj = model(*row[index_start:aggregate_start], **{'__entity_exists': True})
File "/Users/Lucy/Code/Git/spudder/spudmart/src/spudmart/campusrep/models.py", line 51, in __init__
self.user = user
File "/Users/Lucy/Code/Git/spudder/spudmart/src/django/db/models/fields/related.py", line 331, in __set__
self.field.name, self.field.rel.to._meta.object_name))
ValueError: Cannot assign "4661929301770240L": "Student.user" must be a "User" instance.
答案 0 :(得分：0)
在仔细观察追溯 - 我本来应该首先做的 - 我尝试评论出代码以覆盖__init__方法。瞧，它有效！故事的道德：在询问互联网之前，仔细观察追溯。感谢大家的帮助！
答案 1 :(得分：0)
你在模型__init__中做了一些奇怪的事情，你需要将所有这些逻辑移到save()方法，必须是这样的：
class Student(models.Model):
def level(self):
return get_max_triangle_num_less_than(self.rep / STUDENT_REP_LEVEL_MODIFIER)
user = models.ForeignKey(User, unique=True)
school = models.ForeignKey(School)
isHead = models.BooleanField()
referral_code = models.CharField(max_length=128, unique=True)
referred_by = models.ForeignKey(User, blank=True, null=True)
rep = models.IntegerField(default = 0)
def __str__(self):
something = str(self.user.username)
if self.isHead:
something += ", Head at "
else:
something += ", at "
something += self.school.name + ", " + str(self.rep) + " rep points"
return something
def save(self, *args, **kwargs):
if self.pk is None: # if this is new object (not update)
self.school.num_students += 1
self.referral_code = str(uuid.uuid4())
instance = super(Student, self).save(*args, **kwargs)
return instance