为什么 {% if post.is_liked %} 在家里不起作用.html

Question

我已经将is_liked的上下文从PostListView传递到主模板，但是为什么语句if post.is_liked不起作用？我有一个like_post功能，当用户喜欢帖子时，is_liked will equal to true和文本将从不喜欢变为喜欢。但是为什么 if 语句在模板中不起作用(仅显示不喜欢(而没有错误消息？或者我试图将 if 语句更改为{% post.user.is_liked %}和{% user.is_liked %}.但是还是没用，有什么问题？谢谢

models.py

class Post(models.Model):
title = models.CharField(max_length=100)
date_posted = models.DateTimeField(default=timezone.now)
author = models.ForeignKey(User, on_delete=models.CASCADE)
likes = models.ManyToManyField(User, related_name='likes', blank=True)
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse('post-detail', kwargs={'pk': self.pk})

views.py

def home(request):
context = {
'posts': Post.objects.all(),
}
return render(request, 'blog/home.html', context)

def like_post(request):   # post like
post = get_object_or_404(Post, id=request.POST.get('post_id'))
is_liked = False
if post.likes.filter(id=request.user.id).exists():
post.likes.remove(request.user)
is_liked = False
else:
post.likes.add(request.user)
is_liked = True
return HttpResponseRedirect(post.get_absolute_url())

class PostListView(ListView):
model = Post
template_name = 'blog/home.html'  # <app>/<model>_<viewtype>.html
context_object_name = 'posts'
ordering = ['-date_posted']
paginate_by = 10
is_liked = False
def get_context_data(self, *, object_list=None, **kwargs):
context = super(PostListView, self).get_context_data()
posts = context['posts']
for post in posts:
if post.likes.filter(id=self.request.user.id).exists():
context['is_liked'] = True
return context

class PostDetailView(DetailView):
model = Post
is_liked = False
def get_context_data(self, **kwargs):
context = super().get_context_data(**kwargs)
post = context['post']
if post.likes.filter(id=self.request.user.id).exists():
context['is_liked'] = True
return context

首页.html

{% for post in posts %}
<form action="{% url 'like_post' %}" method="post">
{% csrf_token %}
{% if post.is_liked %} #I want to get whether the post is_liked by user
<h5>liked</h5>
{% else %}
<h5>not liked</h5>
{% endif %}
</form>
{% endfor %}

Answer 1

你可以对查询集进行注释，以便由此产生的Post对象有一个额外的属性.is_liked，带有一个Exists子查询 [Django-doc]：

from django.db.models importExists,OuterRef
class PostListView(ListView):
model = Post
template_name = 'blog/home.html'
context_object_name = 'posts'
ordering = ['-date_posted']
paginate_by = 10
def get_queryset(self, *args, **kwargs):
return super().get_queryset(*args, **kwargs).annotate(
is_liked=Exists(Post.likes.through.objects.filter(
user_id=self.request.user.id,
post_id=OuterRef('pk')
))
)