Question

我正在尝试为某机构中基于Web的课程计划应用程序的数据库记录。我担心的是，由于在views.py中的关系M2M而无法在中间表中进行记录，但是它在浏览器的shell中有效我有一个 ValueError：用于精确查找的QuerySet值必须限于使用切片的一种结果。

回溯切换到复制和粘贴视图

C:\Program Files\Python37\lib\site-packages\django\core\handlers\exception.py in inner

                response = get_response(request)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\core\handlers\base.py in _get_response

                    response = self.process_exception_by_middleware(e, request)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\core\handlers\base.py in _get_response

                    response = wrapped_callback(request, *callback_args, **callback_kwargs)

     ...
▶ Local vars
E:\PLACORESA\configuration\views.py in departemnent

                cursus = get_object_or_404(Cursus, libelle_cursus=cursus )

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\shortcuts.py in get_object_or_404

            return queryset.get(*args, **kwargs)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\query.py in get

            num = len(clone)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\query.py in __len__

            self._fetch_all()

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\query.py in _fetch_all

                self._result_cache = list(self._iterable_class(self))

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\query.py in __iter__

            results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\sql\compiler.py in execute_sql

                sql, params = self.as_sql()

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\sql\compiler.py in as_sql

                    where, w_params = self.compile(self.where) if self.where is not None else ("", [])

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\sql\compiler.py in compile

                sql, params = node.as_sql(self, self.connection)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\sql\where.py in as_sql

                    sql, params = compiler.compile(child)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\sql\compiler.py in compile

                sql, params = node.as_sql(self, self.connection)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\lookups.py in as_sql

            rhs_sql, rhs_params = self.process_rhs(compiler, connection)

     ...
▶ Local vars
C:\Program Files\Python37\lib\site-packages\django\db\models\lookups.py in process_rhs

                        'The QuerySet value for an exact lookup must be limited to '

     ...
▶ Local vars

models.py

class Departement(models.Model):
    code_departement=models.CharField("code du département", max_length=100, unique=True)
    libelle_departement=models.CharField("Libellé du département", max_length=100)
    faculte=models.ForeignKey("Faculte", on_delete=models.CASCADE)
    cursus=models.ManyToManyField("Cursus", through="AvoirCursus")   

class Cursus(models.Model):
    code_cursus=models.CharField("Code du cursus", max_length=10, unique=True)
    libelle_cursus=models.CharField("Libellé du cursus", max_length=100) 

class AvoirCursus(models.Model):
    cursus=models.ForeignKey("Cursus", on_delete=models.CASCADE)
    departement=models.ForeignKey("Departement", on_delete=models.CASCADE)

views.py

if request.method == 'POST':
        f = forms.Departement_Form(request.POST)
        if f.is_valid():
            dept = f.save(commit=False)
            code_departement = f.cleaned_data['code_departement'].upper()
            dept.code_departement = code_departement
            cursus = f.cleaned_data['cursus']
            dept.save()
            cursus = get_object_or_404(Cursus, libelle_cursus=cursus )

            AvoirCursus(departement=dept, cursus=cursus)

            return redirect('configuration:lister_departement')

Answer 1

您确定诅咒对象的获取正确吗？也许表单的诅咒会返回多个值或字符串？

此外，尝试在get_or_404之后添加print（cursus）并查看内部内容。

您到底想在这里做什么？

AvoirCursus（部门=部门，cursus = cursus）

确定不应该吗？

AvoirCursus.objects.create（departement = dept，cursus = cursus）

？

没有堆栈跟踪就很难弄清楚。

Answer 2

我已经成功解决了我的问题。视图中使用的表单是来自models.py的通用表单。当我打印（cursus）时，结果是一个包含选定项目的查询集。要编写中间数据库，我进行了“ cursus”过程以拥有不同的对象。

**the views.py is:**
if f.is_valid():
            dept = f.save(commit=False)
            code_departement = f.cleaned_data['code_departement']
            dept.code_departement = code_departement
            print(code_departement)
            cursus = f.cleaned_data['cursus']
            dept.save()
            for i in cursus:
                AvoirCursus.objects.create(departement=dept, cursus=i)

通过模型将数据添加到M2M

2 个答案: