'str'對象沒有屬性'attname'

Question

我試圖根據標題字段使用get_next_or_previous_by_field來顯示指向下一個和上一個對象的鏈接。 Django 1.6正在向我拋出這個錯誤。模板渲染 'str' object has no attribute 'attname'

錯誤時

錯誤發生在這裏的模板。

{% with next_lesson=lesson.get_next_by_title %}

在這裏，在我的模型。

return self._get_next_or_previous_by_FIELD('title', is_next=True)

這裏是我的模型。

class LessonManager(models.Manager): 
    def all(self): 
     return super(LessonManager, self).filter(active=True) 

class Lesson(models.Model): 
    active = models.BooleanField(default=False) 
    title = models.CharField(max_length=65) 
    slug = models.SlugField(unique=True) 

    objects = LessonManager() 

    def __unicode__(self,): 
     return self.title 

    class Meta: 
     ordering = ['title'] 

    def get_absolute_url(self): 
     return reverse('lesson', args=[str(self.slug)]) 

    def get_next_by_title(self): 
     try: 
      return self._get_next_or_previous_by_FIELD('title', is_next=True) 
     except Lesson.DoesNotExist: 
      return None 

    def get_previous_by_title(self): 
     try: 
      return self._get_next_or_previous_by_FIELD(order='title', is_next=False) 
     except Lesson.DoesNotExist: 
      return None 

這裏是我的模板。

<a class="col-md-6" href="{{ lesson.get_previous_by_title.get_absolute_url }}" title="{% trans "View previous post" %}">&laquo; {{ lesson.get_previous_by_title.title }}</a> 
<a class="col-md-6" href="{{ lesson.get_next_by_title.get_absolute_url }}" title="{% trans "View previous post" %}">&laquo; {{ lesson.get_next_by_title.title }}</a> 

這是完整的追溯請求。

Environment: 


Request Method: GET 
Request URL: /tutorials/lesson/lesson-name/ 

Django Version: 1.6.2 
Python Version: 2.7.6 
Installed Applications: 
('django.contrib.admin', 
'django.contrib.auth', 
'django.contrib.contenttypes', 
'django.contrib.sessions', 
'django.contrib.messages', 
'django.contrib.staticfiles', 
'blog', 
'ckeditor', 
'tutorials') 
Installed Middleware: 
('django.contrib.sessions.middleware.SessionMiddleware', 
'django.middleware.common.CommonMiddleware', 
'django.middleware.csrf.CsrfViewMiddleware', 
'django.contrib.auth.middleware.AuthenticationMiddleware', 
'django.contrib.messages.middleware.MessageMiddleware', 
'django.middleware.clickjacking.XFrameOptionsMiddleware') 
Template error: 
In template C:\Users\Shaun\Desktop\sg\static\templates\tutorials\lesson.html, error at line 22 
    'str' object has no attribute 'attname' 
    12 :  {% endif %} 


    13 :  {% if lesson.get_next_by_timestamp %} 


    14 :   <a class="right" href="{{ lesson.get_next_post.get_absolute_url }}">{{ lesson.get_next_post.title|truncatewords:'4' }} &raquo;</a> 


    15 :  {% endif %} 


    16 : 


    17 :  <div class='clearfix'></div> 


    18 : 


    19 :  <h2>{{ lesson.title|upper }}</h2> 


    20 :  <p>{{ lesson.content|safe }}</p> 


    21 :  


    22 :  <a class="col-md-6" href=" {{ lesson.get_previous_by_title.get_absolute_url }} " title="{% trans "View previous post" %}">&laquo; {{ lesson.get_previous_by_title.title }}</a> 


    23 : <a class="col-md-6" href="{{ lesson.get_next_by_title.get_absolute_url }}" title="{% trans "View previous post" %}">&laquo; {{ lesson.get_next_by_title.title }}</a> 


    24 : 


    25 : {% endblock %} 

Traceback: 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\core\handlers\base.py" in get_response 
    114.      response = wrapped_callback(request, *callback_args, **callback_kwargs) 
File "C:\Users\Shaun\Desktop\sg\src\tutorials\views.py" in single_lesson 
    13.  return render_to_response('tutorials/lesson.html', locals(), context_instance=RequestContext(request)) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\shortcuts\__init__.py" in render_to_response 
    29.  return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\loader.py" in render_to_string 
    169.   return t.render(context_instance) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in render 
    140.    return self._render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in _render 
    134.   return self.nodelist.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in render 
    840.     bit = self.render_node(node, context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\debug.py" in render_node 
    78.    return node.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\loader_tags.py" in render 
    123.   return compiled_parent._render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in _render 
    134.   return self.nodelist.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in render 
    840.     bit = self.render_node(node, context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\debug.py" in render_node 
    78.    return node.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\loader_tags.py" in render 
    62.    result = block.nodelist.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in render 
    840.     bit = self.render_node(node, context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\debug.py" in render_node 
    78.    return node.render(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\debug.py" in render 
    88.    output = self.filter_expression.resolve(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in resolve 
    585.     obj = self.var.resolve(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in resolve 
    735.    value = self._resolve_lookup(context) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\template\base.py" in _resolve_lookup 
    789.        current = current() 
File "C:\Users\Shaun\Desktop\sg\src\tutorials\models.py" in get_previous_by_title 
    64.    return self._get_next_or_previous_by_FIELD('title', is_next=False) 
File "C:\Users\Shaun\Desktop\sg\lib\site-packages\django\db\models\base.py" in _get_next_or_previous_by_FIELD 
    708.   param = force_text(getattr(self, field.attname)) 

Exception Type: AttributeError at /tutorials/lesson/setting-up-your-django-blog-application/ 
Exception Value: 'str' object has no attribute 'attname' 

Answer 1

_get_next_or_previous_by_FIELD不應該是你自稱的東西。

你遇到的主要問題是它期望一個Field對象，而不是一個字符串，因此錯誤。這是因爲該方法實際上被用作由字段類自身創建的curried函數的一部分，而該類自身在模型首次導入時又由模型元類調用。

柯里化創建實際的get_next_by_foo和get_previous_by_foo方法。實際上，這些只是爲日期和日期時間字段創建的。

請注意，uncurried方法名稱以下劃線開頭，除了Model._meta之外，這是一個好兆頭，您不應該在自己的代碼中使用它。