django中models聯合唯一unique_together

例：

文章點贊

class ArticleUpDown(models.Model):
    """
    點贊表
    """
    nid = models.AutoField(primary_key=True)
    user = models.ForeignKey(to="UserInfo", null=True, on_delete=models.CASCADE)
    article = models.ForeignKey(to="Article", null=True, on_delete=models.CASCADE)
    is_up = models.BooleanField(default=True)

    class Meta:
        unique_together = (("article", "user"),)
        verbose_name="點贊"
        verbose_name_plural=verbose_name

意思為在這個表中，每一行的user、artical字段必須唯一，否則報錯。