Generic django forms

My last post presented a way of generating dynamic classes in python. Today I would like to present a way of applying this mechanism to Django forms, making them a bit generic. An example may be a login form, that may be used with an "accept regulations" checkbox or without it, depending on the context.

class LoginForm(forms.Form):
    username = forms.CharField(max_length=20, label="Username")
    password = forms.CharField(widget=forms.\
            PasswordInput(render_value=False),max_length=20, label="Password")

    def clean(self):
        #form validation/clean implementation
        pass

This a simplest login form you can get, all there is to do is to implement a login mechanism (or simply use it, it's available at the django.contrib.auth module). Both provided fields are required, so the is_valid method will generate an appropriate result. Now let's make a possibility to generate this form with an "accept regulations" which is also required.

class LoginForm(forms.Form):
    username = forms.CharField(max_length=20, label="Username")
    password = forms.CharField(widget=forms.\
            PasswordInput(render_value=False),max_length=20, label="Password")


    def clean(self):
        #form validation/clean implementation
        pass


    @classmethod
    def with_accept_regulations(cls):
        return type(
            "%sWithAcceptRegulations" % cls.__name__,
            (cls,),
            {"accept_regulations" : forms.BooleanField(required=True, \
                    label="I accept the regulations")},

Now we may easily obtain a login form with accept regulations using the with_accept_regulations class method. Example usage is presented below:

if something:
    CurrentLoginForm = LoginForm
else:
    CurrentLoginForm = LoginForm.with_accept_regulations()


form = CurrentLoginForm(request.POST)
if form.is_valid():
    #and os on...
    pass

This example is trivial, and a similar outcome may be achieved by using simpler mechanisms, however examples are suppose to be simple. This method may be applied to more demanding applications, a huge feature is the ability to chain class creation methods, for example you could try implementing the following:

LoginForm.with_accept_regulations().with_skin_selection(), which would generate a class LoginFormWithAcceptRegulationsWithSkinSelection. I know this is starting to look like java, but the long names are meant to be descriptive :-)



Have fun exploring new possibilities.

Cheers!
KR

P.S.
I was in a hurry, so the code may have some simple mistakes - beware :-)