Django’s built-in template tags are simply Python functions which means they can be used in places other than templates such as class-based views.
Here’s an example using pluralize:
Reading the Django docs for working with class-based views, modelforms, and ajax left me with more than a few questions on how to properly architect them. After much trial and error I’ve landed on what I think is a good, re-usable structure.
The following will walk through a fairly complex example that uses modelforms, an ajax response mixin, some ajax helper methods, and exception middleware.
Let’s start off with a basic model:
As you can see we have just a single field, name. Now let’s create the modelform:
The reason I’m created my own modelform rather than allowing Django to auto-generate one for me is that I’d like to set the max_length parameter on the field and control which fields are updated when the model is saved. This comes in very handy when working with larger models where you only want to write a subset of fields to the database.
It’s worth noting here that even though I’ve specified only the name field in the Meta class’s fields, Django will still update all fields when saving the model unless you explicitly declare the fields to update using update_fields.
Next is the view:
The view is doing a couple of very important things:
You could also require authentication for this view by using this mixin.
Let’s look at the mixin:
This is a simple mixin that overrides the default form_invalid and form_valid functions to return json instead of their usual HttpResponse and HttpResponseRedirect, respectively. A couple of key things are happening in this mixin:
Now let’s have a look at the helper methods:
The first method, get_object_or_json404, is a replacement for django.shortcuts.get_object_or_404() and allows json to be returned with a 404 error. It makes use of a custom exception, JsonNotFound, which we’ll look at shortly.
The second helper method, render_to_json_response, converts the context to json (using a third helper method, convert_context_to_json), sets the content type to application/json, and returns everything using HttpResponse.
The custom exception allows us to trap record not found errors and return an error message as json as well. Here’s the exception:
And here’s the middleware necessary to include the custom exception in your application (you don’t have to get this fancy with an error code and timestamp, but the 404 status and descriptive error message are a must):
Ensure the middleware is added to your application settings:
Finally, let’s create a new route for our class-based view (in urls.py):
Lots to digest but hopefully this is straightforward and easy to implement. If you have any suggestions for improvements, please let me know in the comments.