Django，保存ModelForm

Question

我創建了一個模型學生，它從Django用戶擴展，是另一個模型的外鍵，而它有一個稱爲year的整數字段。我想要做的是保存一個表單，其中有2個字段。一個是當然編號和另一個是整數字段年。當我點擊提交時，出現錯誤無法指定「u'2'」：「Student.course」必須是「課程」實例。

models.py

class Student(models.Model): 
    user = models.OneToOneField(User) 
    course = models.ForeignKey(Course) 
    year = models.IntegerField(validators=[MinValueValidator(1), 
              MaxValueValidator(7)]) 

view.py

def step3(request): 
    user = request.user 
    if request.method == 'POST': 
     form = SelectCourseYear(request.POST) 
     if form.is_valid(): 
      form.save() 
      return render_to_response("registration/complete.html", RequestContext(request)) 
    else: 
     form = SelectCourseYear() 
    return render(request, 'registration/step3.html',) 

forms.py

class SelectCourseYear(forms.ModelForm): 
    course = forms.CharField() 
    year = forms.IntegerField(required=True) 

    class Meta: 
     model = Student 
     fields = ['user', 'course', 'year'] 

Answer 1

你不需要重新定義字段中ModelForm如果你已經在fields提到他們一個實例屬性。所以，你的形式應該是這樣的 -

class SelectCourseYear(forms.ModelForm): 
    class Meta: 
     model = Student 
     fields = ['course', 'year'] # removing user. we'll handle that in view 

我們可以輕鬆處理視圖的形式 -

def step3(request): 
    user = request.user 
    if request.method == 'POST': 
     form = SelectCourseYear(request.POST) 
     if form.is_valid(): 
      student = form.save(commit=False) 
      # commit=False tells Django that "Don't send this to database yet. 
      # I have more things I want to do with it." 

      student.user = request.user # Set the user object here 
      student.save() # Now you can send it to DB 

      return render_to_response("registration/complete.html", RequestContext(request)) 
    else: 
     form = SelectCourseYear() 
    return render(request, 'registration/step3.html',) 

Answer 2

course必須是一個場模型的實例，而不僅僅是主實例的關鍵。您仍然可以接受表單中的ID作爲文本輸入，但您需要檢索實際課程實例並分配值。

您需要驗證課程ID是否有效，因此將該代碼放入乾淨的方法並不是一個壞主意。還請注意course字段在這裏排除？否則，表單會期望它存在。您也不需要重新定義year字段，因爲ModelForm將從Student模型繼承該字段。

# forms.py 

class SelectCourseYear(forms.ModelForm): 
    class Meta: 
     model = Student 
     exclude = ['user', 'course'] 

    course_id = forms.IntegerField() 

    def __init__(self, *args, **kwargs): 
     self.user = kwargs.pop('user') 
     super(SelectCourseYear, self).__init__(*args, **kwargs) 

    def clean_course_id(self): 
     course_id = self.cleaned_data.get('course_id') 
     try: 
      self.course = Course.objects.get(pk=course_id) 
     except Course.DoesNotExist: 
      raise forms.ValidationError('Sorry, that course id is not valid.') 

     return course_id 

    def save(self, commit=True): 
     instance = super(SelectCourseYear, self).save(commit=False) 
     instance.course = self.course 
     instance.user = self.user 
     if commit: 
      instance.save() 
     return instance 


# views.py 

def step3(request): 
    if request.method == 'POST': 
     form = SelectCourseYear(request.POST or None, user=request.user) 
     if form.is_valid(): 
      form.save() 
      return render_to_response("registration/complete.html", 
       RequestContext(request)) 
    return render(request, 'registration/step3.html',) 

現在，當你在模型上調用.save()，課程場將被分配的Course