项目：设置优先级

本课属于 Coddy Django 学习旅程的“JSON API”单元。第 15 课，共 19 课。

现在该由你自己添加一个功能了。每项任务都有一个priority：low、normal或high。API 应该允许程序请求一种优先级，并阻止任何人自行添加第四种。

你已经有了所有需要的内容：用于筛选的request.GET.get()、可以多次筛选的 QuerySet，以及在返回 400 时一并发送的errors字典。

允许的值定义在模型中。Task.Priority是一个TextChoices类，而Task.Priority.values是列表["low", "normal", "high"]。对它进行检查，就意味着以后在模型中添加优先级时，无需修改视图也能接受该值。

挑战

中等

在 tasks/views.py 的 task_list 中添加优先级。?priority=high 只会列出高优先级任务，也可以和 ?done= 一起使用：?priority=high&done=false。如果 POST 请求中的优先级不是 low、normal 或 high，则不会保存任何内容，并会返回 400，错误字典中的消息类似于 {"errors": {"priority": "Choose low, normal or high."}}。未指定优先级时，默认值仍为 normal。

点击“运行”：预览会打开 /api/tasks/?priority=high，并列出 Write the report。

亲手试试

import json

from django.http import HttpResponse, JsonResponse
from django.shortcuts import get_object_or_404, render
from django.utils.decorators import method_decorator
from django.views import View
from django.views.decorators.csrf import csrf_exempt
from django.views.decorators.http import require_GET, require_http_methods

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")


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


def task_row(request, pk):
    task = get_object_or_404(Task, pk=pk)
    return render(request, "tasks/list.html#task-row", {"task": task})


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


@csrf_exempt
@require_http_methods(["GET", "POST"])
def task_list(request):
    if request.method == "POST":
        try:
            data = json.loads(request.body)
        except json.JSONDecodeError:
            return JsonResponse({"error": "The body is not valid JSON."}, status=400)
        errors = {}
        title = data.get("title", "").strip()
        if not title:
            errors["title"] = "This field is required."
        if errors:
            return JsonResponse({"errors": errors}, status=400)
        task = Task.objects.create(
            title=title,
            priority=data.get("priority", "normal"),
        )
        return JsonResponse(task_to_dict(task), status=201)
    tasks = Task.objects.all()
    done = request.GET.get("done")
    if done == "true":
        tasks = tasks.filter(done=True)
    elif done == "false":
        tasks = tasks.filter(done=False)
    return JsonResponse([task_to_dict(task) for task in tasks], safe=False)


def not_found():
    return JsonResponse({"error": "Task not found"}, status=404)


@method_decorator(csrf_exempt, name="dispatch")
class TaskDetail(View):
    def get(self, request, pk):
        task = Task.objects.filter(pk=pk).first()
        if task is None:
            return not_found()
        return JsonResponse(task_to_dict(task))

    def patch(self, request, pk):
        task = Task.objects.filter(pk=pk).first()
        if task is None:
            return not_found()
        data = json.loads(request.body)
        if "title" in data:
            task.title = data["title"]
        if "done" in data:
            task.done = data["done"]
        task.save()
        return JsonResponse(task_to_dict(task))

    def delete(self, request, pk):
        task = Task.objects.filter(pk=pk).first()
        if task is None:
            return not_found()
        task.delete()
        return HttpResponse(status=204)