Filter with a Query

Part of the JSON APIs section of Coddy's Django journey. Lesson 4 of 19.

A program often wants part of the list: only the open tasks, say. APIs take such options in the query string, the part of the URL after ?. You read it with request.GET.get(), which gives None when the option is missing, so the plain URL keeps listing everything. The starter's task_list now builds its list with task_to_dict, from a QuerySet you can narrow. A bookshop filtering /api/books/?genre=poetry:

books = Book.objects.all()
genre = request.GET.get("genre")
if genre:
    books = books.filter(genre=genre)

A yes or no option needs more care. Everything in a URL is text, so ?done=false gives the string "false", and every non-empty string is true. if done: cannot tell yes from no: compare the text with each word you expect, and give each word its own filter.

Challenge

Easy

Let /api/tasks/ filter by done:

?done=true lists only the done tasks.
?done=false lists only the tasks not done.
No query still lists every task.

Press Run: the preview opens /api/tasks/?done=false and lists two tasks.

Try it yourself

from django.http import JsonResponse
from django.shortcuts import render

from .models import Task


def task_to_dict(task):
    return {
        "id": task.id,
        "title": task.title,
        "done": task.done,
        "priority": task.priority,
    }


def home(request):
    return render(request, "tasks/home.html", {"tasks": Task.objects.all()})


def stats(request):
    data = {
        "total": Task.objects.count(),
        "done": Task.objects.filter(done=True).count(),
    }
    return JsonResponse(data)


def task_list(request):
    tasks = Task.objects.all()
    return JsonResponse([task_to_dict(task) for task in tasks], safe=False)


def task_detail(request, pk):
    task = Task.objects.filter(pk=pk).first()
    if task is None:
        return JsonResponse({"error": "Task not found"}, status=404)
    return JsonResponse(task_to_dict(task))