Working with URLs

As soon as you write a plugin that provides a new view to the user (or if you want to contribute to pretix itself), you need to understand how URLs work in pretix as it differs slightly from the standard Django system.

The reason for the complicated URL handling is that pretix supports custom subdomains for single organizers. In this example we will use an event organizer with the slug bigorg that manages an awesome conference with the slug awesomecon. If pretix is installed on pretix.eu, this event is available by default at https://pretix.eu/bigorg/awesomecon/ and the admin panel is available at https://pretix.eu/control/event/bigorg/awesomecon/.

If the organizer now configures a custom domain like tickets.bigorg.com, his event will from now on be available on https://tickets.bigorg.com/awesomecon/. The former URL at pretix.eu will redirect there. However, the admin panel will still only be available on pretix.eu for convenience and security reasons.

URL routing

The hard part about implementing this URL routing in Django is that https://pretix.eu/bigorg/awesomecon/ contains two parameters of nearly arbitrary content and https://tickets.bigorg.com/awesomecon/ contains only one. The only robust way to do this is by having separate URL configuration for those two cases. In pretix, we call the former our maindomain config and the latter our subdomain config. For pretix’s core modules we do some magic to avoid duplicate configuration, but for a fairly simple plugin with only a handful of routes, we recommend just configuring the two URL sets separately.

The file urls.py inside your plugin package will be loaded and scanned for URL configuration automatically and should be provided by any plugin that provides any view.

A very basic example that provides one view in the admin panel and one view in the frontend could look like this:

from django.conf.urls import url

from . import views

urlpatterns = [
    url(r'^control/event/(?P<organizer>[^/]+)/(?P<event>[^/]+)/mypluginname/',
        views.AdminView.as_view(), name='backend'),
]

event_patterns = [
    url(r'^mypluginname/', views.FrontendView.as_view(), name='frontend'),
]

Note

As you can see, the view in the frontend is not included in the standard Django urlpatterns setting but in a separate list with the name event_patterns. This will automatically prepend the appropriate parameters to the regex (e.g. the event or the event and the organizer, depending on the called domain).

If you only provide URLs in the admin area, you do not need to provide a event_patterns attribute.

URL reversal

pretix uses Django’s URL namespacing feature. The URLs of pretix’s core are available in the control and presale namespaces, there are only very few URLs in the root namespace. Your plugin’s URLs will be available in the plugins:<applabel> namespace, e.g. the form of the email sending plugin is available as plugins:sendmail:send.

Generating a URL for the frontend is a complicated task, because you need to know whether the event’s organizer uses a custom URL or not and then generate the URL with a different domain and different arguments based on this information. pretix provides some helpers to make this easier. The first helper is a python method that emulates a behavior similar to reverse:

pretix.multidomain.urlreverse.eventreverse(obj, name, kwargs=None)

Works similar to django.core.urlresolvers.reverse but takes into account that some organizers or events might have their own (sub)domain instead of a subpath.

Non-keyword arguments are not supported as we want do discourage using them for better readability.

Parameters:

• obj – An Event or Organizer object

• name (str) – The name of the URL route

• kwargs – A dictionary of additional keyword arguments that should be used. You do not need to provide the organizer or event slug here, it will be added automatically as needed.

Returns:

An absolute URL (including scheme and host) as a string

In addition, there is a template tag that works similar to url but takes an event or organizer object as its first argument and can be used like this:

{% load eventurl %}
<a href="{% eventurl request.event "presale:event.checkout" step="payment" %}">Pay</a>

Implementation details

There are some other caveats when using a design like this, e.g. you have to care about cookie domains and referrer verification yourself. If you want to see how we built this, look into the pretix/multidomain/ sub-tree.