django 主鍵要與自己行成多對一的關係時可以用models.foreignkey('self'),如果直接儲存會提示主鍵不存在,無法儲存.

例如:我想做一個導航類,這些導航儲存著自己的父節點,一開始寫法為:

class Navi(models.Model): """ Navi has four type: goods, news, page and custom """ STYLE_CHOICES = ( ('goods', 'goods'), ('news', 'news'), ('page', 'page'), ('custom', 'custom'), ) name = models.SlugField() parent = models.ForeignKey('self', null=True, blank=True, related_name='child') style = models.SlugField(choices=STYLE_CHOICES) url = models.CharField(max_length=100, default='#') sort = models.IntegerField(default=1) is_display = models.BooleanField(default=True) def __unicode__(self): return self

該做法無論如何都無法儲存第一個資料的,因為你在儲存第一個資料時它的主鍵還未產生,無法形成多對一關係.修改方法如下:

class AbstractNavi(models.Model): parent = models.ForeignKey('self',blank=True, null=True, related_name='child') class Meta: abstract = True class Navi(AbstractNavi): """ Navi has four type: goods, news, page and custom """ STYLE_CHOICES = ( ('goods', 'goods'), ('news', 'news'), ('page', 'page'), ('custom', 'custom'), ) name = models.SlugField() #parent = models.ForeignKey('self', null=True, blank=True, related_name='child') style = models.SlugField(choices=STYLE_CHOICES) url = models.CharField(max_length=100, default='#') sort = models.IntegerField(default=1) is_display = models.BooleanField(default=True) def __unicode__(self): return self.name

定義抽象類AbstractNavi, 讓Navi類繼承自AbstractNavi.