django:相关字段查找无效

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'

当我尝试运行以下查询时

User.objects.filter(student_attending__studentclasshistory__year=2011)

我收到错误 Related Field has invalid lookup: year .这很奇怪，因为我省略了年份，可用字段是 Cannot resolve keyword '' into field. Choices are: attended_class, id, semester, student, year
怎么会这样？

另外，还有 through在我的模型属性中，我可以删除 related_name ?

Answer 1

问题是 year is a field lookup ，所以 Django 认为您试图从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 的 year 成为可调用的，即:

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

)