How can I change a Django form field value before saving?

问题

if request.method == 'POST':
    userf = UsersModelForm(request.POST)
    username = userf.data['username']
    password = userf.data['password']
    passwordrepeat = userf.data['passwordrepeat']
    email = userf.data['email']

I tried this:

    tempSalt = bcrypt.gensalt()
    password = bcrypt.hashpw(password,tempSalt)
    passwordrepeat = bcrypt.hashpw(passwordrepeat,tempSalt)

    userf.data['password'] = password
    userf.data['passwordrepeat'] = passwordrepeat

But i got error. How can i change the value of userf.data['password'] and userf.data['passwordrepeat'] before saving?

Error:

AttributeError at /register

This QueryDict instance is immutable

Request Method:     POST
Request URL:    http://127.0.0.1:8000/register
Django Version:     1.3.1
Exception Type:     AttributeError
Exception Value:    

This QueryDict instance is immutable

Exception Location:     /usr/local/lib/python2.6/dist-packages/django/http/__init__.py in _assert_mutable, line 359
Python Executable:  /usr/bin/python
Python Version:     2.6.6
Python Path:    

['/home/user1/djangoblog',
 '/usr/lib/python2.6',
 '/usr/lib/python2.6/plat-linux2',
 '/usr/lib/python2.6/lib-tk',
 '/usr/lib/python2.6/lib-old',
 '/usr/lib/python2.6/lib-dynload',
 '/usr/local/lib/python2.6/dist-packages',
 '/usr/lib/python2.6/dist-packages',
 '/usr/lib/python2.6/dist-packages/gst-0.10',
 '/usr/lib/pymodules/python2.6',
 '/usr/lib/pymodules/python2.6/gtk-2.0']

回答1:

If you need to do something to the data before saving, just create a function like:

def clean_nameofdata(self):
    data = self.cleaned_data['nameofdata']
    # do some stuff
    return data

All you need is to create a function with the name **clean_***nameofdata* where nameofdata is the name of the field, so if you want to modify password field, you need:

def clean_password(self):

if you need to modify passwordrepeat

def clean_passwordrepeat(self):

So inside there, just encrypt your password and return the encrypted one.

I mean:

def clean_password(self):
    data = self.cleaned_data['password']
    # encrypt stuff
    return data

so when you valid the form, the password would be encrypted.

回答2:

See the documentation for the save() method

if request.method == 'POST':
    userf = UsersModelForm(request.POST)
    new_user = userf.save(commit=False)

    username = userf.cleaned_data['username']
    password = userf.cleaned_data['password']
    passwordrepeat = userf.cleaned_data['passwordrepeat']
    email = userf.cleaned_data['email']

    new_user.password = new1
    new_user.passwordrepeat = new2

    new_user.save()

回答3:

You will have problems if you need to fill form from POST, change any form field value and render form again. Here is solution for it:

class StudentSignUpForm(forms.Form):
  step = forms.IntegerField()

  def set_step(self, step):
    data = self.data.copy()
    data['step'] = step
    self.data = data

And then:

form = StudentSignUpForm(request.POST)
if form.is_valid() and something():
  form.set_step(2)
  return  render_to_string('form.html', {'form': form})

回答4:

Override _clean methods and put your checks in them. You can modify cleaned_data from there.

E.g:

def clean_password(self):
    new1 = self.cleaned_data['password']
    return new1

Every fields in the form will have a field_name_clean() method created automatically by Django. This method is called when you do form.is_valid().

回答5:

The problem with the previous solutions is, that it will not work if validation fails. In order to avoid validation, you can use the instance:

instance = form.instance
instance.user = request.user
instance.save()

But be careful, this does not check is_valid(). If you want to do that, you can instantiate the form with the new values:

# NOT TESTED, NOT SURE IF THIS WORKS...
form = MyForm(instance=instance)
if form.is_valid():
    form.save()

来源：https://stackoverflow.com/questions/8924993/how-can-i-change-a-django-form-field-value-before-saving

标签

python

django

forms

model

save