Django CreateView的表单没有按预期重新呈现

Question

我正在尝试创建一个表单，其中当从下拉菜单中选择另一个字段title时，会预先填充某个字段checkin_type。我正在尝试遵循Django: How to pre-populate FormView with dynamic (non-model) data?中概述的方法，并在此处设置了“概念验证”项目：https://github.com/khpeek/django-dynamic-form。

在视图的模板中，我已经这样做了，当checkin_type字段有.change()时，会发送一个AJAX POST请求，其中包含所选签入的id类型：

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/js-cookie@2/src/js.cookie.min.js"></script>
<script>
    $(document).ready(function(){
        var csrftoken = Cookies.get('csrftoken');

        function csrfSafeMethod(method) {
            // these HTTP methods do not require CSRF protection
            return (/^(GET|HEAD|OPTIONS|TRACE)$/.test(method));
        }
        $.ajaxSetup({
            beforeSend: function(xhr, settings) {
                if (!csrfSafeMethod(settings.type) && !this.crossDomain) {
                    xhr.setRequestHeader("X-CSRFToken", csrftoken);
                }
            }
        });

        $(".auto-submit").change(function() {
            $.post({
                url: "{% url 'checkin-create' %}",
                data: {id: $(".auto-submit option:selected").val()}
            })
        });
    });
</script>


<form action="" method="post">{% csrf_token %}
    {% for field in form %}
        <div class="{% if field.name == 'checkin_type' %}auto-submit{% endif %}">
            {{ field.errors }}
            {{ field.label_tag }}
            {{ field }}
        </div>
    {% endfor %}
    <input type="submit" value="Send message" />
</form>

在views.py中，我尝试了以下内容：

import logging
import sys

from django.views import generic
from .models import CheckIn, CheckInType

from django.http import HttpResponse


def get_stdout_logger(name, level):
    logger = logging.getLogger(name)
    logger.setLevel(level)

    handler = logging.StreamHandler(sys.stdout)
    handler.setLevel(level)
    formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
    handler.setFormatter(formatter)
    logger.addHandler(handler)
    return logger


logger = get_stdout_logger(__name__, level=logging.DEBUG)


class CheckInCreate(generic.CreateView):
    model = CheckIn
    fields = '__all__'

    def post(self, request, *args, **kwargs):
        if request.is_ajax():
            logger.debug(f"Received AJAX POST request with the following request.POST data: {request.POST}")
            self.checkin_type = CheckInType.objects.get(pk=request.POST['id'])
        return super().post(request, *args, **kwargs)

    def get_initial(self):
        initial = super().get_initial()
        if hasattr(self, 'checkin_type'):
            initial.update(title=self.checkin_type.title)
        logger.debug(f"Getting initial: {initial}")
        return initial

    def form_valid(self, *args, **kwargs):
        logger.debug("The form is valid!")
        return super().form_valid(*args, **kwargs)

    def form_invalid(self, form):
        logger.debug("The form is invalid!")
        if hasattr(self, 'checkin_type'):
            form['title'].initial = self.checkin_type.title
            logger.debug(f"The form's initial title is now {form['title'].initial}")
        return super().form_invalid(form)

现在，如果我python manage.py runserver，请导航至localhost:8000/checkins/new，然后从checkin_type下拉菜单中选择一个选项，我会看到预期的记录结果：

System check identified no issues (0 silenced).
March 01, 2018 - 21:02:14
Django version 2.0.1, using settings 'my_project.settings'
Starting development server at http://127.0.0.1:9000/
Quit the server with CONTROL-C.
2018-03-01 21:02:18,595 - dashboard.views - DEBUG - Getting initial: {}
[01/Mar/2018 21:02:18] "GET /checkins/new HTTP/1.1" 200 2200
2018-03-01 21:02:26,015 - dashboard.views - DEBUG - Received AJAX POST request with the following request.POST data: <QueryDict: {'id': ['2']}>
2018-03-01 21:02:26,018 - dashboard.views - DEBUG - Getting initial: {'title': '2-week check-in'}
2018-03-01 21:02:26,018 - dashboard.views - DEBUG - The form is invalid!
2018-03-01 21:02:26,018 - dashboard.views - DEBUG - The form's initial title is now 2-week check-in
[01/Mar/2018 21:02:26] "POST /checkins/new HTTP/1.1" 200 2259

但是，我没有看到表格中的变化！调用super().form_invalid(form)是否应该重新呈现修改后的表单？