Django两个自我引用的外键

Question

在Django 1.7中编写一个简单的应用程序.是表示链接列表元素的模型:

class TrainingUserWordSetItem(models.Model):
    training_set = models.ForeignKey(TrainingUserWordSet)
    user_word = models.ForeignKey(UserWord)
    prev_item = models.ForeignKey("TrainingUserWordSetItem", null=True, default=None)
    next_item = models.ForeignKey("TrainingUserWordSetItem", null=True, default=None)

迁移时我收到错误:

hellodict.TrainingUserWordSetItem.next_item: (fields.E304) Reverse accessor for 'TrainingUserWordSetItem.next_item' clashes with reverse accessor for 'TrainingUserWordSetItem.prev_item'.
        HINT: Add or change a related_name argument to the definition for 'TrainingUserWordSetItem.next_item' or 'TrainingUserWordSetItem.prev_item'.
hellodict.TrainingUserWordSetItem.prev_item: (fields.E304) Reverse accessor for 'TrainingUserWordSetItem.prev_item' clashes with reverse accessor for 'TrainingUserWordSetItem.next_item'.
        HINT: Add or change a related_name argument to the definition for 'TrainingUserWordSetItem.prev_item' or 'TrainingUserWordSetItem.next_item'.

如何使两个自我指涉的外键领域？

更新:

帮助使用related_name ='+':

class TrainingUserWordSetItem(models.Model):
    training_set = models.ForeignKey(TrainingUserWordSet)
    user_word = models.ForeignKey(UserWord)
    prev_item = models.ForeignKey("TrainingUserWordSetItem", null=True, default=None)
    next_item = models.ForeignKey("TrainingUserWordSetItem", null=True, default=None, related_name='+')

Answer 1

你实际上可能完成了你在一个领域尝试的东西.我相信这会奏效:

next_item = models.ForeignKey('self', null=True, default=None, related_name='prev_item')

注意使用'self'; 根据Django文档,To create a recursive relationship – an object that has a many-to-one relationship with itself – use models.ForeignKey('self').

另外,我建议尝试使用OneToOneField而不是ForeignKey,假设每个项目只有一个前一个项目和一个下一个项目.