从子类的ModelForm创建父类对象

Question

I have a Model 'Appointment'. In that class patient is associated with built-in User model.I have made a modelform for that class. Is it possible to instantiate an object of another class (User in field patient) from inside the same form. I am not able to access User Model's field in the form. How can this be done ?

class Appointment(models.Model):
    doctor = models.ForeignKey(Doctor)
    clinic = models.ForeignKey(Clinic, null=True, blank=True)
    hospital = models.ForeignKey(Hospital, null=True, blank=True)
    day = models.DateField()
    time = models.TimeField()
    patient = models.ForeignKey(User)

I have created a ModelForm for this model as below:

class HospitalCreateAppointmentForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(HospitalCreateAppointmentForm, self).__init__(*args, **kwargs)
        for field in iter(self.fields):
                self.fields[field].widget.attrs.update({
                    'class': 'form-control'
                })

    class Meta:
        model = Appointment
        fields = ['doctor','hospital','day','time','patient']
        widgets = {
            'day': forms.SelectDateWidget(),
        }

Answer 1

I am not sure purpose behind instantiating user object in HospitalCreateAppointmentForm . However, just in case you really need, you have to import User model in form file. For example if your HospitalCreateAppointmentFor is in forms.py , import User module like

from django.contrib.auth.models import User

And you can access field like:

User._meta.fields