如何验证Django 1.7中的下拉菜单？

Question

I have a Django Form that doesn't record the Dropdown value when I create a validation. Instead the validation reads the value as always being null. This thus triggers the validation:

This field cannot be null.

What could I be doing wrong? I am new to the Django framework, so any help would be appreciated. Here is my forms.py file:

from django import forms 
from reviews.models import Rating, Review

CHOICES = (
    (1,'One Star'),
    (2,'Two Star'),
    (3,'Three Star'),
    (4,'Four Star'),
    (5,'Five Star')
)

SERVICES = (
(0, 'Select a Service Name or Start typing'),
(85, 'Service1'),
(86, 'Service2'),
(88, 'Service3'),
(89, 'Service4'),
(90, 'Service5')
)

class ReviewForm(forms.ModelForm):
    serv_id = forms.ChoiceField(required=True, choices= SERVICES, widget=forms.Select(attrs={'class':'form-control'}))
    rating_value = forms.ChoiceField(required = True, choices = CHOICES,  widget=forms.RadioSelect(attrs={'class' : ''}))
    review_text = forms.CharField(required=True, widget=forms.Textarea(attrs={'class' : 'form-control', 'placeholder': 'Write Review', 'rows':5}))

    class Meta:
        model = Review
        fields = ('rating_value', 'review_text', 'serv_id',)

    def clean_serv_id(self):
        serv_id = self.cleaned_data['serv_id']
        if serv_id <= 0:
            raise forms.ValidationError("You need to select a Service.")

As long as a user selects an option from the drop down (id integer value) it works. The problem is that the validation doesn't get triggered when the id = 0 (the user doesn't select a service):

Answer 1

You need to return the value from clean_serv_id .

def clean_serv_id(self):
    serv_id = self.cleaned_data['serv_id']
    if serv_id <= 0:
        raise forms.ValidationError("You need to select a Service.")
    else:
        return serv_id

Answer 2

I was going to post this a lot earlier.. The issue was that my comparison operator in my validation was incorrect-- oh and I definitely needed to return serv_id, I just removed it from the original code after trying to debug for some reason.. Apparently, the numerical value 0 that I used as a value in my widget is interpreted as "0" in the ChoiceField.

Here is the validation that works. Notice that I also had to change the comparison operator to "==":

def clean_serv_id(self):
        serv_id = self.cleaned_data['serv_id']
        if serv_id == "0":
            raise forms.ValidationError("You need to select a Service.")
        else:
            return serv_id