A Full Event

Part of the Forms section of Coddy's Django journey. Lesson 17 of 20.

The Pottery Class has 2 places and 2 guests, yet its form still takes more. The rule belongs in the form, but only the view knows which event the form is for.

A form is a Python class, so you can give it your own __init__. Take the extra value as a keyword argument, keep it on self, and pass the rest to super().__init__(). A bid form that needs the auction item:

class BidForm(forms.Form):
    amount = forms.IntegerField()

    def __init__(self, *args, item=None, **kwargs):
        super().__init__(*args, **kwargs)
        self.item = item

    def clean_amount(self):
        amount = self.cleaned_data["amount"]
        if amount <= self.item.top_bid:
            raise forms.ValidationError("Bid more than the top bid.")
        return amount

The view passes the item each time it builds the form: BidForm(request.POST, item=item). Naming item in the signature keeps it out of **kwargs; Django's form does not know it and would raise TypeError.

Challenge

Medium

Full events refuse RSVPs.

In events/forms.py, give RSVPForm an __init__ that keeps a keyword argument event on self.event and passes the rest to super().__init__.
In its clean(), when guests fill the capacity, raise Sorry, this event is full. One place left still takes a guest.
In event_detail, pass event to both RSVPForm calls.

RSVP to the Pottery Class: you see Sorry, this event is full.

Try it yourself

import datetime

from django import forms

from .models import RSVP, Event


class EventForm(forms.ModelForm):
    class Meta:
        model = Event
        fields = ["title", "date", "end_date", "place", "description", "capacity"]

    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


class RSVPForm(forms.ModelForm):
    class Meta:
        model = RSVP
        fields = ["name", "email"]