视图和模板中的Django模型关系

Question

I'm working on multi-user rss reader. I want to limit display of posts only to those which are unread. I've managed to do this in my single "feed" view as below, but I can't figure out how to do the same in multiple feed aka "category" view.

I've been trying something like here https://docs.djangoproject.com/en/1.5/topics/db/queries/#spanning-multi-valued-relationships but it didn't work for me

Should I change my "category" view code or template code? and if so how would you go about it?

thanks! -S

models

class UserCategory(models.Model):
    name = models.CharField(unique=False, max_length=64)
    user = models.ForeignKey(User)
    slug = AutoSlugField(populate_from='name', always_update='True', unique_with='user')

class Feed(models.Model):
    feed_url = models.URLField(unique=True)
    default_title = models.CharField(max_length=64, blank=True)
    link = models.URLField(blank=True)

class UserFeed(models.Model):
    feed = models.ForeignKey(Feed)
    title = models.CharField(max_length=64)
    category = models.ForeignKey(UserCategory)
    user = models.ForeignKey(User)
    slug = AutoSlugField(populate_from='title', always_update='True', unique_with='user')

class Post(models.Model):
    feed = models.ForeignKey(Feed)
    title = models.CharField(max_length=256)
    content = models.TextField()
    link = models.URLField(max_length=512)

class ReadPost(models.Model):
    user = models.ForeignKey(User)
    post = models.ForeignKey(Post)

views

def feed(request, user_feed_slug):
    user_feed = get_object_or_404(UserFeed.objects.filter(slug=user_feed_slug, user=request.user))
    read_post = ReadPost.objects.filter(user=request.user).values_list('post')
    posts = Post.objects.select_related().filter(feed=user_feed.feed).exclude(id__in=read_post)

def category(request, user_category_slug):
    user_category = get_object_or_404(UserCategory.objects.filter(slug=user_category_slug, user=request.user)) 

templates

feed
    {% for post in posts %}
        {{ post.title }}                    
    {% endfor %}

category
{% for feed in user_category.userfeed_set.all %}
    {{ feed.title }}
    {% for post in feed.feed.post_set.all %}
        {{ post.title }}
        {{ post.content }}
    {% endfor %}
{% endfor %}

Answer 1

You can write custom template filter , ie:

@register.filter
def unread(posts, read_posts):
    return posts.exclude(id__in=read_posts)

(before you must pass read_post to category template context).

Answer 2

Try this queryset:

def category(request, user_category_slug):
    user_category = get_object_or_404(UserCategory, slug=user_category_slug,
                                           user=request.user))

    feeds = UserFeed.objects.filter(category__slug=user_category_slug, user=request.user)\
                .prefetch_related('feed__post_set')

then in your template:

{% for feed in feeds %}
    {{ feed.title }}
    {% for post in feed.feed.post_set.all %}
        {{ post.title }}
        {{ post.content }}
    {% endfor %}
{% endfor %}