Django Tutorial: Calendar App - Part III

Alerts

The next feature I’ll add will be a sidebar with alerts about upcoming events. For the sake of simplicity we’ll only show tomorrow’s and today’s events, but it’d be very easy to make this a configurable setting.

Since we would like to see the alerts on all pages, I’ll add the sidebar to base.html template; our function will be reminders() and it will be called in both yearly and monthly view:

def reminders(request):
    """Return the list of reminders for today and tomorrow."""
    year, month, day = time.localtime()[:3]
    reminders = Entry.objects.filter(date__year=year, date__month=month,
                                   date__day=day, creator=request.user, remind=True)
    tomorrow = datetime.now() + timedelta(days=1)
    year, month, day = tomorrow.timetuple()[:3]
    return list(reminders) + list(Entry.objects.filter(date__year=year, date__month=month,
                                   date__day=day, creator=request.user, remind=True))

We’re using timedelta() again to find out tomorrow’s date; list() function is a Python built-in that converts querysets to simple lists because querysets can’t be added to one another otherwise. In main() function, reminders have to be passed on to the template:

return render_to_response("cal/main.html", dict(years=lst, user=request.user, year=year,
                                               reminders=reminders(request)))

Add the same change to month(), as well, and add the following section to base.html:

{% if reminders %}
<div class="reminders">
    <div class="gr">Alerts</div>
    {% for reminder in reminders %}<p> {{ reminder.short|safe }}</p>
    {% endfor %}
</div>
{% endif %}

I checked the remind box in tomorrow’s entry and here it is, in huge red letters!

Settings Page

The next feature I’d like to add is a very simple settings screen with just a single option: whether to show other users’ events or not. The url, function and template will all be called settings:

(r"^settings/$", "settings"),

def _show_users(request):
    """Return show_users setting; if it does not exist, initialize it."""
    s = request.session
    if not "show_users" in s:
        s["show_users"] = True
    return s["show_users"]

@login_required
def settings(request):
    """Settings screen."""
    s = request.session
    _show_users(request)
    if request.method == "POST":
        s["show_users"] = (True if "show_users" in request.POST else False)
    return render_to_response("cal/settings.html", add_csrf(request, show_users=s["show_users"]))

The setting will be stored in user’s session; I have added a small utility function that will set show_users the first time it’s called. In settings() I’m using a Python construct you may be unfamiliar with: myvar = x if <condition> else y. Brackets are optional; I find the construct very expressive and handy but an if/else block would work just as well.

The template is almost too easy:

<h4>Settings</h4>
<form action="" method="POST"> {% csrf_token %}
Show other users' entries:
    <input type="checkbox" name="show_users" {% if show_users %}checked{% endif %} />
<input type="submit" value="Save" />
</form>

And, last but not least, we do need to make use of the setting in all three views we have:

# main()

entries = Entry.objects.filter(date__year=y, date__month=n+1)
if not _show_users(request):
    entries = entries.filter(creator=request.user)

# month() is exactly the same!

# day()
other_entries = []
if _show_users(request):
    other_entries = Entry.objects.filter(date__year=year, date__month=month,
                                   date__day=day).exclude(creator=request.user)

return render_to_response("cal/day.html", add_csrf(request, entries=formset, year=year,
        month=month, day=day, other_entries=other_entries, reminders=reminders(request)))

In day() we’re using exclude() method — we haven’t used it before — it’s similar to filter() except that it removes matching records from queryset.

The other_entries will be listed on top of the day view:

{% for entry in other_entries %}
    <div class="entry">
    {{ entry.creator }} |
    {{ entry.short|safe }}<br />
    {{ entry.body }}<br />
    </div>
{% endfor %} <br />

We can see other users’ entries because that option is on at this time:

...and in daily view:

Hope you liked the Calendar Tutorial. Here are some things you may want to do as an exercise: add an option to the settings page to show the alert X days before the event; add times to events; have an option to have more than one user associated with an event — or think of something else entirely!

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