A ModelForm

Part of the Forms section of Coddy's Django journey. Lesson 12 of 20.

Look at EventForm and the Event model side by side: the same fields, written twice. A ModelForm builds its fields from the model. For a Book model:

from .models import Book


class BookForm(forms.ModelForm):
    class Meta:
        model = Book
        fields = ["title", "author", "pages"]

The inner Meta class names the model and the fields to use. Each model field becomes the matching form field, and blank=True makes it optional. The list is required, so a field added to the model later never reaches a public form by accident.

clean_<field>() and clean() work the same beside Meta. And the form saves itself: form.save() creates the row from cleaned_data and returns it.

Challenge

Easy

Turn EventForm into a ModelForm:

Its fields come from Event: title, date, end_date, place, description, capacity.
The field lines go; clean_date() and clean() stay.
new_event lets the form create the event.

Press Run and add an event.

Try it yourself

import datetime

from django import forms


class EventForm(forms.Form):
    title = forms.CharField(max_length=100)
    date = forms.DateField()
    end_date = forms.DateField(required=False)
    place = forms.CharField(max_length=100)
    description = forms.CharField(widget=forms.Textarea, required=False)
    capacity = forms.IntegerField(min_value=1)

    def clean_date(self):
        date = self.cleaned_data["date"]
        if date < datetime.date.today():
            raise forms.ValidationError("The date cannot be in the past.")
        return date

    def clean(self):
        cleaned_data = super().clean()
        date = cleaned_data.get("date")
        end_date = cleaned_data.get("end_date")
        if date and end_date and end_date < date:
            raise forms.ValidationError("The event cannot end before it starts.")
        return cleaned_data