Django的：相关领域具有无效查找

Question

我有以下型号

class SchoolClass(models.Model): 
    id = models.AutoField(primary_key = True) 
    class_name = models.TextField() 
    level = models.IntegerField() 
    taught_by = models.ManyToManyField(User,related_name="teacher_teaching",through='TeachSubject') 
    attended_by = models.ManyToManyField(User,related_name='student_attending',through='StudentClassHistory') 

    def __unicode__(self): 
     return self.class_name 
    class Meta: 
     db_table = 'classes' 

class StudentClassHistory(models.Model): 
    student = models.ForeignKey(User) 
    year = models.IntegerField(default=datetime.date.today().year) 
    semester = models.IntegerField() 
    attended_class = models.ForeignKey(SchoolClass) 

    class Meta: 
     db_table = 'student_class_history' 

当我尝试运行下面的查询

User.objects.filter(student_attending__studentclasshistory__year=2011) 

我得到了错误Related Field has invalid lookup: year。这很奇怪，因为我省略了一年，可用字段为Cannot resolve keyword '' into field. Choices are: attended_class, id, semester, student, year

这是怎么回事？

此外，与through在我的模型属性中，我可以只删除related_name？

Answer 1

问题是，year is a field lookup，所以Django认为你试图从某个不是日期的东西中提取年份。你应该写：

User.objects.filter(student_attending__studentclasshistory__year__exact=2011) 

（另外，你应该让default用于year可调用，即：

year = models.IntegerField(default=lambda: datetime.date.today().year) 

）