On Fri, Sep 11, 2015 at 7:37 AM, <gengshengh...@gmail.com> wrote:
> Example: I have 2 <input> on a html page, which is a form (assume it is
> login form, with username and password, both are required and will do
> validation on this.).
>
> The behavior of is_valid I see is:
> When submit, the returned errors for the form are:
> This field is required (for username)
> This field is required (for password)
> We'll usually render these messages for the fields (example: {{ form }} will
> automatically do all these).
>
> Now, my question is, it seems like is_valid will trigger validation on both
> username and password every time? How to stop it in case one field cannot
> pass the validation? Does it make sense to validate all these always? I
> think in some of web pages, the behaviour we see is, when one field does not
> fulfill the requirements, it give an error message for this only, and when
> user submit again but the next field does not fulfill the requirement, it
> give error for this field.
>
> Current behaviour in django:
> user name: .....(input box)
> password: ....(input box)
> Submit without any value, we get:
> user name: .....(input box) This field is required
> password: ....(input box) This field is required
>
> I expect:
> user name: .....(input box) This field is required
> password: ....(input box) (No error here)
>
> If username is entered and password is empty, submit again, we'll get:
> user name: what you enter here (input box)
> password: ....(input box) This field is required
>
> Any idea how to achieve this?
>
"required" means "always required", but you wish to only have the
password required when the username is also provided.
Therefore, set password as not required, and add a check in clean()
that applies your special logic and assigns the error message to the
appropriate field.
Eg:
def clean(self):
data = super(MyForm, self).clean()
user = data.get('username')
password = data.get('password')
if user and not password:
self.add_error('password', 'This field is required')
See also:
https://docs.djangoproject.com/en/1.8/ref/forms/validation/#cleaning-and-validating-fields-that-depend-on-each-other
Cheers
Tom
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