添加ManytoManyField打破Django的

Question

在我的項目，我有一個模型，項目，即在保存時創建另一個模型，Access，它包含了manytomanyfield，一個access_list，用戶可以將其他用戶添加到他們的合作者項目。它的工作原理 - 當我創建一個新的項目，我可以添加其他用戶到它，但如果我添加第二個用戶，這將不再擔任該網頁有錯誤，

Exception Value: get() returned more than one Access -- it returned 2!" 

如果我切換到一個帳戶我已添加到該項目中，然後使用該帳戶添加其他用戶，他們添加的很好，並且不會破壞頁面。

當分頁符，它也創造了我的項目頁面上的項目的其他實例，即使只有一個數據庫項目的實例。

我的代碼：

Models.py：

class Project(models.Model): 
    created_by = models.ForeignKey(User) 

    super(Project, self).save() 
    Access.objects.get_or_create(project=self) 

class Access(models.Model): 
    project = models.ForeignKey(Project) 
    access_list = models.ManyToManyField(User) 
    pubdate = models.DateTimeField(default=timezone.now) 

Views.py：

@login_required 
def access(request, project_id=1): 
thisuser = request.user 
if Access.objects.filter(Q(access_list=thisuser) | Q(project__created_by=thisuser), project__id=project_id).exists(): 
     accesspermission = Access.objects.filter(Q(access_list=thisuser) | Q(project__created_by=thisuser), project__id=project_id).order_by('-project__project_pubdate')[0] 
    else: 
     accesspermission = None 
    if Entry.objects.filter(project_id=project_id).exists(): 
     anyentries = Entry.objects.filter(project_id=project_id, entry_unique=1).order_by('-entry_pubdate')[0] 
    else: 
     anyentries = None 
    if Entry.objects.filter(project_id=project_id, entry_unique=1).exists(): 
     firstentry = Entry.objects.filter(project_id=project_id, entry_unique=1).order_by('-entry_pubdate')[0] 
    else: 
     firstentry = None 
    if Entry.objects.filter(project_id=project_id).exists(): 
     lastentry = Entry.objects.filter(project_id=project_id).order_by('-entry_pubdate')[0] 
     lastentrynumber = lastentry.entry_unique 
    else: 
     lastentrynumber = None 
if request.method == "POST":  
    form = AddAccessForm(request.POST) 
    if form.is_valid(): 
     p = form.save(commit=False) 

     adduserfromform = p.accessupdate 
     if User.objects.filter(username=adduserfromform).exists(): 
      usertoadd = User.objects.get(username=adduserfromform) 
      projecttoadd = Access.objects.filter(project__id=project_id).order_by('-project__project_pubdate')[0] 
      projecttoadd.access_list.add(usertoadd) 
     else: 
      usertoadd = None 

     removeuserfromform = p.accessremove 
     if User.objects.filter(username=removeuserfromform).exists(): 
      usertoremove = User.objects.get(username=removeuserfromform) 
      projecttoremove = Access.objects.filter(project__id=project_id).order_by('-project__project_pubdate')[0] 
      projecttoremove.access_list.remove(usertoremove) 
     else: 
      usertoremove = None 

     form.save() 

     return HttpResponseRedirect('/projects/get/%s/access' % project_id) 

回溯：

Traceback (most recent call last): 
    File "/webapps/filmeditdb/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 114, in get_response 
    response = wrapped_callback(request, *callback_args, **callback_kwargs) 
    File "/webapps/filmeditdb/local/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view 
    return view_func(request, *args, **kwargs) 
    File "/webapps/filmeditdb/filmeditdb/docproject/views.py", line 284, in access 
    def access(request, project_id=1): 
    File "/webapps/filmeditdb/local/lib/python2.7/site-packages/django/db/models/manager.py", line 151, in get 
    return self.get_queryset().get(*args, **kwargs) 
    File "/webapps/filmeditdb/local/lib/python2.7/site-packages/django/db/models/query.py", line 310, in get 
    (self.model._meta.object_name, num)) 
MultipleObjectsReturned: get() returned more than one Access -- it returned 2! 
2014-03-25 22:48:26 [17264] [INFO] Handling signal: winch 
2014-03-25 22:48:26 [17264] [INFO] SIGWINCH ignored. Not daemonized 

Answer 1

添加完整回溯一般特別建議，但是來自錯誤s hown問題是最有可能在這條線：

projecttoremove = Access.objects.get(project__id=project_id).order_by('-project__project_pubdate')[0] 

Django的get()總是預計返回只有 1對象。如果有0個對象，則拋出異常，如果超過0則拋出MultipleObjectsReturned異常。

更改了該行早前線在這裏匹配：

projecttoadd = Access.objects.filter(project__id=project_id).order_by('-project__project_pubdate')[0] 

如果做不到這一點，找出錯誤的調用。你得到的例外很清楚。 在代碼中的某些時候，你在呼喚Access.objects.get()一些參數，它是尋找2個的對象，而不是1.請修正參數，或MOER可能切換爲使用filter()。