I'm currently working on a model that has been already built and i need to add some validation managment. (accessing to two fields and checking data, nothing too dramatic)
I was wondering about the exact difference between models and forms at a validation point of view and if i would be able to just make a clean method raising errors as in a formview in a model view ?
- for extra knowledge, why are thoses two things separated ?
And finnaly, what would you do ? There are already some methods written for the model and i don't know yet if i would rewrite it to morph it into a form and simply add the clean() method + i don't exactly know how they work.
Oh, and everything is in the admin interface, havn't yet worked a lot on it since i started django not so long ago.
Thanks in advance,
You should use model (field) validation to make sure the returning datatype meets your database's requirements. Usually you won't need this because django's builtin fields do this for you, so unless you've built some custom field or know what you are doing you shouldn't change things.
Form validation is where you clean the user's input, you can add a clean method for every form field by adding a clean_FIELD(self) method, e.g.
class ContactForm(forms.Form):
# Everything as before.
...
def clean_recipients(self):
data = self.cleaned_data['recipients']
if "fred@example.com" not in data:
raise forms.ValidationError("You have forgotten about Fred!")
# Always return the cleaned data, whether you have changed it or
# not.
return data
Before a Form's main clean method is ran, it checks for a field level clean for each of its fields
Generally models represent business entities which may be stored in some persistent storage (usually relational DB). Forms are used to render HTML forms which may retreive data from users.
Django supports creating forms on the basis of models (using ModelForm class). Forms may be used to fetch data which should be saved in persistent storage, but that's not only the case - one may use forms just to get data to be searched in persistent storage or passed to external service, feed some application counters, test web browser engines, render some text on the basis of data entered by user (e.g. "Hello USERNAME"), login user etc.
Calling save() on model instance should guarantee that data will be saved in persistent storage if and only data is valid - that will provide consistent mechanism of validation of data before saving to persistent storage, regardless whether business entity is to be saved after user clicks "Save me" button on web page or in django interactive shell user will execute save() method of model instance.
