Django form not calling custom validator - django

Question

I'm using Django 2.0. This is my forms.py:
class PostcodeForm(forms.Form):
postcode = forms.CharField(required=True, widget=forms.TextInput(
attrs={
'placeholder': "enter a postcode",
}
))
def clean_postcode(self):
postcode = self.clean_data.get('postcode', '')
print('clean_postcode', postcode)
if postcode != 'something':
raise forms.ValidationError(_("Please enter a valid postcode"), code='invalid')
return data
And my views.py:
def index(request):
form = PostcodeForm()
context = {
'form': form
}
return render(request, 'index.html', context)
And my index.html:
<form class="form-inline" id="lookup_postcode" action="{% url 'lookup_postcode' %}" method="get">
{% csrf_token %}
{{ form.non_field_errors }}
{{ form.postcode.errors }}
{{ form.postcode }}
<button type="submit">Submit</button>
</form>
But when I type in any value other than 'something', the form still submits. I also don't see any print statements in the console, so it looks as though the validator just isn't being run.
What am I doing wrong?

Answer 1

At the moment you are always doing form = PostcodeForm(), for GET and POST requests. That means that the form is not bound to any data, so it will never be valid or have any errors.
In Django, a typical view to process a form looks something like this:
from django.shortcuts import redirect
def index(request):
if request.method == 'POST':
form = PostcodeForm(request.POST)
if form.is_valid():
# form is valid. Process form and redirect
...
return redirect('/success-url/')
else:
form = PostcodeForm()
context = {
'form': form
}
return render(request, 'index.html', context)
For this to work, you'll need to change your form method to 'post'.
<form class="form-inline" id="lookup_postcode" action="{% url 'lookup_postcode' %}" method="post">
If you keep the form method as 'get' then you'll need to bind the form to request.GET instead. You might want to add a check, otherwise you'll get errors for required fields when you first access the index view.
if 'postcode' in request.GET:
# bound form
form = PostcodeForm(request.GET)
else:
# unbound, empty form
form = PostcodeForm()

Answer 2

Use your form as below:
class PostcodeForm(forms.Form):
postcode = forms.CharField(required=True, widget=forms.TextInput(
attrs={
'placeholder': "enter a postcode",
}
))
def clean(self):
postcode = self.cleaned_data.get('postcode', '')
print('clean_postcode', postcode)
if postcode != 'something':
raise forms.ValidationError(_("Please enter a valid postcode"), code='invalid')
return super(PostcodeForm, self).clean()

Answer 3

Everytime you deal with the validity of the posted data, make sure to include form.is_valid() condition in your views.py.