Django的：無法保存相關模型CBV

Question

我有兩個機型非常相似，this case：

class Location(models.Model): 
    city = models.CharField(max_length=20) 
    address = models.CharField(max_length=30) 

class Event(models.Model): 
    location = models.ForeignKey(Location)  
    date = models.DateField() 
    user = models.ForeignKey(User) 

我試圖在形式保存這些對象：

class EventForm(forms.ModelForm): 
    city = forms.CharField(label=_('City'), max_length=30) 
    address = forms.CharField(label=_('Street'), max_length=30, required=False) 

    class Meta: 
     model = Event 

    def __init__(self, *args, **kwargs) 
     super(EventForm, self).__init__(*args, **kwargs) 
     try: 
      self.fields['city'].initial = self.instance.location.city 
      self.fields['address'].initial = self.instance.location.street 
     except AttributeError: 
      pass 

    def save(self, commit=True): 
     event = super(EventForm, self).save(commit=False) 
     location = event.location 
     location.city = self.cleaned_data['city'] 
     location.address = self.cleaned_data['address'] 
     location.save() 
     return event 

這將引發錯誤'NoneType' object has no attribute 'city'

我也嘗試在CBV中保存位置：

class EventEdit(UpdateView): 
    model = Event 

    def form_valid(self, form): 
     event = form.save(commit=False) 
     location = event.location 
     location.city = self.cleaned_data['city'] 
     location.address = self.cleaned_data['address'] 
     location.save() 
     event.save() 
     return HttpResponseRedirect(self.get_success_url()) 

同樣，同樣的錯誤'NoneType' object has no attribute 'city'

在基於類的視圖中保存相關對象的正確方法是什麼？

更新

我要補充一點，我想諮詢一下更新現有的位置分配給事件。添加新事件位置在EventCreate(CreateView)中完成，與完全相同，建議使用Rohan。

class EventCreate(CreateView): 
    def form_valid(self, form): 
     self.object = form.save(commit=False) 
     location = Location() 
     location.address = self.request.POST['address'] 
     location.city = self.request.POST['city'] 
     location.save() 
     self.object.location = location 
     self.object.save() 
     return HttpResponseRedirect(self.get_success_url()) 

Answer 1

在你save方法event.location將None。您需要創建location 實例，然後將其保存。

更新：爲了節約現有對象：

我不知道你的UpdateView實施辦法讀Generic views - Models

去後我會建議改變的觀點爲：

class EventEdit(UpdateView): 
    model = Event 

    def form_valid(self, form): 
     #instance trying to update 
     event = form.instance 
     location = event.location 
     if location == None: 
      location = Location() 
     location.city = self.cleaned_data['city'] 
     location.address = self.cleaned_data['address'] 
     location.save() 
     event.location = location 
     #event.save() instead of this do 
     super(EventEdit, self).form_valid(form) 
     return HttpResponseRedirect(self.get_success_url()) 

---

舊解決方案：

我會更改保存方法爲

def save(self, commit=True): 
    event = super(EventForm, self).save(commit=False) 
    location = Location() 
    location.city = self.cleaned_data['city'] 
    location.address = self.cleaned_data['address'] 
    location.save() 
    event.location = location 
    event.save() 
    return event