Question

In my django app, I have these models

class Lesson(models.Model):
    name = models.CharField(max_length=200)
    course = models.ForeignKey(Course)
    ...
class Course(models.Model):
    title = models.CharField(max_length=200)
    ...

I use two forms to get/create a Course instance in my Edit_Lesson template.In one choice_form I use a ModelChoiceField to create a dropdown list in the template.In the other course_name_form I provide a textfield by using CharField where the user can enter a course name.

I need to do the validation for these.If initially there are no courses ie Course.objects.all() is an empty list,the drop down list in choice_form will not have any items for the user to select from.Then,if user forgets to enter a name in the textfield of course_name_form,there wont be any course instance selected/created.When this happens I would like to show the user an error message asking him to input a course name.

I think ,I won’t be able to write the validation code in the forms.Should I create a error_list=[] in my view and put the error in it and display it?This means ,the validation happens in view.I am not sure if this is the right way

please advise

Answer 1

You can override the clean() method of your model forms to perform validation that requires knowledge of a broader scope.

In your case, you might do

def clean(self):
   if not Course.objects.count() and not self.cleaned_data['course_name']:
       raise ValidationError(u"Some sensible message")
   return self.cleaned_data