如何优雅地改进Django中的模板碎片缓存详解

{% load cache %}
{% cache 500 sidebar %}
 .. sidebar ..
{% endcache %}

def test_view(request):
 # code...
 sidebar = get_data()
 return render(reqeust, 'test_view.html', {'sidebar': sidebar})

from django.core.cache import cache
def get_data():
 key = 'hot-course'
 result = cache.get(key)
 if result:
 return result
 # 比较耗时的数据获取
 result = Course.objects.filter().order_by('-fav_num')[:10]
 cache.set(key, result, 600) # 保存至缓存
 return result

class UserCacheNode(Node):
 """
 优雅的自定义模板碎片缓存
 """
 def __init__(self, nodelist, expire_time_var, fragment_name, vary_on, cache_name, fun=None):
 # ...
 self.fun = fun # 用于数据获取的回调函数

 def render(self, context:dict):
 # ...
 if value is None:
  if self.fun: # 实行回调
  context.update(self.fun(*vary_on))
  value = self.nodelist.render(context)
  fragment_cache.set(cache_key, value, expire_time) # 保存至缓存
 return value

def get_hot_course():
 # 做会调用，函数返回字典
 print("call hot course")
 hot_courses = Course.objects.filter().order_by('stu_nums')[:5]
 return locals()

@register.tag('hot_course_cache') # 自定义的标签名称
def hot_course_cache(parser, token):
 nodelist = parser.parse(('endcache',))
 parser.delete_first_token()
 tokens = token.split_contents()
 cache_name = None

 return UserCacheNode(
 nodelist, parser.compile_filter(tokens[1]),
 tokens[2], # fragment_name can't be a variable.
 [parser.compile_filter(t) for t in tokens[3:]],
 cache_name,
 fun=get_hot_course, # 回调函数
 )

{% load course_tag %}
{% hot_course_cache 500 hot_courses %}
 ...hot_courses...
{% endcache %}