覆蓋在Django的ModelForm保存（）方法來創建或更新

Question

簡介：

我要重寫保存（）方法，在我的自定義的ModelForm在模型中創建一個新的行或更新一些數據如果它存在。我已經找到了一些解決方案，但它在視圖函數中實現，如鏈接Django form INSERTs when I want it to UPDATE，但我想以save（）方法實現它。

我的模型：

我默認auth.User型號和我的作者模型，如下圖所示，我也有另一種模式叫UserAuthor，用於當它們之間的多對多關係在我的情況下強制要求添加其他領域，如「is_follow」和「審查」

class Author(models.Model): 
    name = models.CharField(max_length=50) 

class UserAuthor(models.Model): 
     user = models.ForeignKey(User, on_delete=models.CASCADE) 
     author = models.ForeignKey(Author, on_delete=models.CASCADE) 
     is_follow = models.BooleanField(default=0) 
     review = models.TextField(max_length=500, blank=True, null=True) 

我的表格：

class ReviewFollowAuthorForm(forms.ModelForm): 
    class Meta: 
     model = UserAuthor 
     fields = ("is_follow", "review") 

    def save(self, commit=True, user=None, author=None): 
     user_author = super(ReviewFollowAuthorForm, self).save(commit=False) 
     user_author.user = user 
     user_author.author = author 
     if commit: 
      user_author.save() 
     return user_author 

筆者認爲：

class ReviewFollowAuthor(View): 
    def post(self, request, **kwargs): 
     user = request.user 
     author = get_object_or_404(Author, id=kwargs['pk']) 
     f = ReviewFollowAuthorForm(request.POST) 
     if(f.is_valid()): 
      f.save(user=user,userx=userx) 
      return JsonResponse({'success':1}) 
     else: 
      return JsonResponse({'success':0}) 

在這種情況下，它在數據庫中爲每個保存（）調用創建一個新的行。我不知道如何在保存之前檢查save方法，只需更新以防在請求者用戶的前一行有作者，我嘗試了許多事情，但是我失敗了。我知道我可以使用：

user_author = UserAuthor.objects.filter(user=user, author=author) 

和更新，如果它返回一個結果，但在save（）方法本身怎麼樣？

Answer 1

使用django queryset get_or_create()方法。

來自文檔：該方法用於查找具有給定kwargs的對象（如果模型具有所有字段的默認值，則可能爲空），如果需要則創建一個。

瞭解更多關於它here in the docs。現在

，您的視圖中：現在

class ReviewFollowAuthor(View): 
    def post(self, request, **kwargs): 
     user = request.user 
     author = get_object_or_404(Author, id=kwargs['pk']) 
     #MAKE certain that user and author always have an instance within them. 
     #send the user, author to the form. 
     f = ReviewFollowAuthorForm(request.POST , user = user , author = author) 
     if(f.is_valid()): 
      f.save(user=user,userx=userx) 
      return JsonResponse({'success':1}) 
     else: 
      return JsonResponse({'success':0}) 

，您的ModelForm中：

class ReviewFollowAuthorForm(forms.ModelForm): 
    def __init__(self, *args, **kwargs): 
     #override __init__ to make your "self" object have the instances sent by the your views.(author and user) 
     self.user = kwargs.pop('user' , None) 
     self.author = kwargs.pop('author' , None) 
     #Now your model-form instance has the user and the author attribute within itself. 
     super(ReviewFollowAuthorForm, self).__init__(*args, **kwargs) 
    class Meta: 
     model = UserAuthor 
     fields = ("is_follow", "review") 

    def save(self, commit=True): 
     user_author, created = UserAuthor.objects.update_or_create(user=self.user, author=self.author, defaults={'is_follow': self.cleaned_data.get('is_follow'), 'review': self.cleaned_data.get('review')}) 
     #rest of your logic 
     return user_author 

我希望這會引導你以某種方式。 謝謝。