Step25: number of posts in category and tag

Author: zmrenwu

README.md

@@ -145,6 +145,7 @@ tutorial 分支为项目的主分支，每一篇教程的代码都和历史提
 22. [在脚本中使用 ORM：Faker 批量生成测试数据](https://www.zmrenwu.com/courses/hellodjango-blog-tutorial/materials/80/)
 23. [通过 Django Pagination 实现简单分页](https://www.zmrenwu.com/courses/hellodjango-blog-tutorial/materials/81/)
 24. [稳定易用的 Django 分页库，完善分页功能](https://www.zmrenwu.com/courses/hellodjango-blog-tutorial/materials/82/)
+25. [统计各个分类和标签下的文章数](https://www.zmrenwu.com/courses/hellodjango-blog-tutorial/materials/83/)
 
 ## 公众号
 <p align="center">

blog/templatetags/blog_extras.py

@@ -1,4 +1,5 @@
 from django import template
+from django.db.models.aggregates import Count
 
 from ..models import Post, Category, Tag
 
@@ -21,13 +22,15 @@ def show_archives(context):
 
 @register.inclusion_tag('blog/inclusions/_categories.html', takes_context=True)
 def show_categories(context):
+    category_list = Category.objects.annotate(num_posts=Count('post')).filter(num_posts__gt=0)
     return {
-        'category_list': Category.objects.all(),
+        'category_list': category_list,
     }
 
 
 @register.inclusion_tag('blog/inclusions/_tags.html', takes_context=True)
 def show_tags(context):
+    tag_list = Tag.objects.annotate(num_posts=Count('post')).filter(num_posts__gt=0)
     return {
-        'tag_list': Tag.objects.all(),
+        'tag_list': tag_list,
     }

templates/blog/inclusions/_categories.html

@@ -3,7 +3,7 @@ <h3 class="widget-title">分类</h3>
   <ul>
     {% for category in category_list %}
       <li>
-        <a href="{% url 'blog:category' category.pk %}">{{ category.name }} <span class="post-count">(13)</span></a>
+        <a href="{% url 'blog:category' category.pk %}">{{ category.name }} <span class="post-count">({{ category.num_posts }})</span></a>
       </li>
     {% empty %}
       暂无分类！

templates/blog/inclusions/_tags.html

@@ -3,7 +3,7 @@ <h3 class="widget-title">标签云</h3>
   <ul>
     {% for tag in tag_list %}
       <li>
-        <a href="{% url 'blog:tag' tag.pk %}">{{ tag.name }}</a>
+        <a href="{% url 'blog:tag' tag.pk %}">{{ tag.name }} <span class="post-count">({{ tag.num_posts }})</a>
       </li>
     {% empty %}
       暂无标签！