Python 3.x django模型实例上的外键约束失败

我尝试在一个动作上创建一个模型实例。我无法让这个过程成功。我收到一条关于外键Constraint失败的错误消息，我被卡住了。 下面是我尝试为模型返回创建模型实例的视图

@login_required(login_url='/login/')
def return_book(request,pk):
    books = Books.objects.filter(school = request.user.school).get(id = pk)
    if books:
        Return.objects.create(borrowed_item_id=books.id,returner_id=request.user.school.id)
    return redirect("view_books")

模型

class Books(models.Model):
    school = models.ForeignKey(School, on_delete=models.CASCADE)
    reg_no = models.CharField(max_length=50)
    book_name = models.CharField(max_length=200)

class Issue(models.Model):
    borrower_id = models.ForeignKey(Student,on_delete=models.CASCADE)
    book_id = models.ForeignKey(Books,on_delete=models.CASCADE)

class Return(models.Model):
    return_date = models.DateField(default=datetime.date.today)
    borrowed_item = models.ForeignKey(Issue,on_delete=models.DO_NOTHING)
    returner = models.ForeignKey(CustomUser,on_delete=models.DO_NOTHING)

还有追踪

Traceback (most recent call last):
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\contrib\auth\decorators.py", line 21, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "D:\Python\Django\test projects\library manage\lib_system\Library-System\libman\views.py", line 216, in return_book
    Return.objects.create(borrowed_item_id=books.id,returner_id=request.user.id)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\query.py", line 447, in create
    obj.save(force_insert=True, using=self.db)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\base.py", line 753, in save
    self.save_base(using=using, force_insert=force_insert,
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\base.py", line 790, in save_base
    updated = self._save_table(
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\base.py", line 895, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\base.py", line 933, in _do_insert
    return manager._insert(
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\query.py", line 1254, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\models\sql\compiler.py", line 1397, in execute_sql
    cursor.execute(sql, params)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\utils.py", line 98, in execute
    return super().execute(sql, params)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\FR GULIK\AppData\Local\Programs\Python\Python38-32\lib\site-packages\django\db\backends\sqlite3\base.py", line 413, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: FOREIGN KEY constraint failed

这是postgresql发布的错误

insert or update on table "libman_return" violates foreign key constraint "libman_return_borrowed_item_id_b84dde78_fk_libman_issue_id"
DETAIL:  Key (borrowed_item_id)=(9) is not present in table "libman_issue".

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returner\u id=request.user.school.id

，这里我看到

returner

是

CustomUser

的外键，但是

request.user.school.id

意味着它是一些模型实例的id，比如

school

（猜猜这里的名字）？也许您需要编写

returner\u id=request.user.id

？它没有显示任何差异。答案是一样的。啊，

借来的项目

是

问题

的外键，但是你给它传递了

书籍

的id（注意：模型名称最好是单数的，因此

书籍

应该是一个更好的名称）例如，看到问题了吗？