Show form in a view based on Django classes

I have the impression that it must be something simple, but I can not do it with CBV's. I try to render a view that shows the content of a post, and at the same time, in the same view, show a form so that comments can be added to it. The first thing I have, not the second, show the form where you add the comments. All my views are based on classes.

models.py

class Comment(models.Model):

    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    comment = models.TextField()
    author = models.ForeignKey(settings.AUTH_USER_MODEL,
                           on_delete=models.CASCADE)

    def get_absolute_url(self):
        return reverse('project_list')

    def __str__(self):
        return self.comment

The view that is supposed to show the form to add comments is very similar to the view used to add a new topic:

views.py

class ProjectDetailView(DetailView):
    model = models.Project
    template_name = 'portfolio/project_detail.html'
    fields = ['comment']

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

In the template I show the detail of the post and at the same time I try to show the form where to add comments, here I lose myself. If I add them from the admin I see them, but not the form.

p_detail.html

<p>{{ project.description|safe }}</p>


{% for comment in project.comment_set.all %}
<div class="comment">
    {{ comment.body|linebreaks }}
</div>
{% empty %}
<p>There are no comments yet.</p>
{% endfor %}

{% if new_comment %}
  <h2>Your comment has been added.</h2>
{% else %}
<h2>Add a new comment</h2>
<form action="." method="post">
     {% csrf_token %}
    {{ form.as_p }}
    <p><input type="submit" value="Add comment">    </p>
</form>
{% endif %}

and this is the url with which I show the detail of the post

urls.py

urlpatterns = [

  path('<int:pk>/', views.ProjectDetailView.as_view(),
     name='project_detail'),

Thank you in advance.

       Environment:


    Request Method: POST
    Request URL: http://127.0.0.1:8000/23/

    Django Version: 2.0.2
    Python Version: 3.6.5
    Installed Applications:
    ['django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'crispy_forms',
    'ckeditor',
    'ckeditor_uploader',
    'core',
    'users',
    'portfolio.apps.PortfolioConfig']
    Installed Middleware:
    ['django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware']



    Traceback:

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
    35.             response = get_response(request)

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
    128.                 response = self.process_exception_by_middleware(e, request)

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
    126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/views/generic/base.py" in view
    69.             return self.dispatch(request, *args, **kwargs)

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/views/generic/base.py" in dispatch
    89.         return handler(request, *args, **kwargs)

    File "/home/rni/workspace/pyt/web-personal/webpersonal/portfolio/views.py" in post
    36.         context = self.get_context_data(*args, **kwargs)

    File "/home/rni/workspace/pyt/web-personal/webpersonal/portfolio/views.py" in get_context_data
    31.         context = super(ProjectDetailView, self).get_context_data(*args, **kwargs)

    File "/home/rni/workspace/pyt/web-personal/env/lib/python3.6/site-packages/django/views/generic/detail.py" in get_context_data
    93.         if self.object:

    Exception Type: AttributeError at /23/
    Exception Value: 'ProjectDetailView' object has no attribute 'object'