Editing an Event

Part of the Forms section of Coddy's Django journey. Lesson 13 of 20.

Each event page now has an Edit this event link to /events/1/edit/. The URL, the link and the template are ready, and edit_event already finds the event the URL names. The rest of the view is yours.

A ModelForm edits an existing row when you hand it that row as instance. For a note in a notes app:

note = get_object_or_404(Note, pk=4)

form = NoteForm(instance=note)                # filled in with the note's values

form = NoteForm(request.POST, instance=note)  # the new values, for this note
if form.is_valid():
    form.save()                               # updates note 4, adds no row

Without data, NoteForm(instance=note) draws the form filled in with the row's current values. With data, instance=note makes form.save() update that row instead of creating a new one.

An edit page needs both. Forget the instance on the GET and the visitor sees an empty form; forget it on the POST and saving adds a copy.

Challenge

Easy

Finish edit_event in events/views.py:

A GET shows the form filled in with the event's details.
A valid POST saves the changes to this event, adds no new one, and redirects to its page.
An invalid POST shows the page again with the errors.

The template needs form and event. Press Run, then press Edit this event.

Try it yourself

from django.shortcuts import get_object_or_404, redirect, render

from .forms import EventForm
from .models import Event


def event_list(request):
    q = request.GET.get("q", "")
    events = Event.objects.all()
    if q:
        events = events.filter(title__icontains=q)
    return render(request, "events/event_list.html", {"events": events, "q": q})


def event_detail(request, pk):
    event = get_object_or_404(Event, pk=pk)
    return render(request, "events/event_detail.html", {"event": event})


def new_event(request):
    if request.method == "POST":
        form = EventForm(request.POST)
        if form.is_valid():
            event = form.save()
            return redirect("events:detail", pk=event.pk)
    else:
        form = EventForm()
    return render(request, "events/new_event.html", {"form": form})


def edit_event(request, pk):
    event = get_object_or_404(Event, pk=pk)
    # Build the form for this event, check it and save it, like new_event.
    return render(request, "events/edit_event.html", {"event": event})