概述：

登入使用者就可以檢視文章詳情，訪客就不能檢視文章詳情並且報錯

報錯程式碼如下：

Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
--以上程式碼基本都是確定訪客身份的--
1
next_topic的值是： <QuerySet [<Topic: Topic object (2)>, <Topic: Topic object (3)>]>
Internal Server Error: /v1/topics/qq66907360
Traceback (most recent call last):
  File 
 
"D:\Program Files (x86)\Python\Python310\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "D:\Program Files (x86)\Python\Python310\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File 
 
"D:\Program Files (x86)\Python\Python310\lib\site-packages\django\views\generic\base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "D:\Program Files (x86)\Python\Python310\lib\site-packages\django\views\generic\base.py", line 101, in dispatch
    return handler(request, *args, **kwargs)
  File 
 
"D:\PycharmProjects\linuxTangblog\topic\views.py", line 151, in get
    res = self.make_topic_res(author,author_topic,is_self)
  File "D:\PycharmProjects\linuxTangblog\topic\views.py", line 29, in make_topic_res
    next_id = next_topic.id if next_topic else None
AttributeError: 'QuerySet' object has no attribute 'id'
[17/Dec/2021 15:02:20] "GET /v1/topics/qq66907360?t_id=1 HTTP/1.1" 500 79151

排查過程：

我遍歷了一下'QuerySet'物件，發現遍歷後的資料是object物件，然後再用object取值就把值取出來了，

next_topic的值是： <QuerySet [<Topic: Topic object (2)>, <Topic: Topic object (3)>]>
next_topic = Topic.objects.filter(id__gt=author_topic.id,author=author,limit='public')
for i in next_topic:
    print(i.id)

然後我就想，上一篇和和下一篇只要一個值，但是顯然這個queryset物件有多個值，不符合預期，然後就看程式碼發現沒有寫first()或last()這個條件

        if is_self:
            #下一篇
            next_topic = Topic.objects.filter(id__gt=author_topic.id,author=author).first()
            #上一篇
            last_topic = Topic.objects.filter(id__lt=author_topic.id,author=author).last()
        else:
            next_topic = Topic.objects.filter(id__gt=author_topic.id,author=author,limit='public')
            last_topic = Topic.objects.filter(id__lt=author_topic.id,author=author,limit='public')

解決辦法：

加上first()或last()這個條件

        if is_self:
            #下一篇
            next_topic = Topic.objects.filter(id__gt=author_topic.id,author=author).first()
            #上一篇
            last_topic = Topic.objects.filter(id__lt=author_topic.id,author=author).last()
        else:
            next_topic = Topic.objects.filter(id__gt=author_topic.id,author=author,limit='public').first()
            last_topic = Topic.objects.filter(id__lt=author_topic.id,author=author,limit='public').last()