Django什么是反向关系？ [英] Django What is reverse relationship?

问题描述

有人可以告诉我反向关系是什么意思吗？
我已经开始使用Django，并且在文档的很多地方都提到了反向关系。到底是什么意思？为什么有用？参考这篇文章？

Can someone tell me what is reverse relationship means? I have started using Django and in lot of places in the documentation I see 'reverse relationship, being mentioned. What is it exactly mean? why is it useful? What does it got to do with related_name in reference to this post ?

推荐答案

以下是 related_name

假设您有2个模型

class Group(models.Model):
    #some attributes

class Profile(models.Model):
    group = models.ForeignKey(Group)
    #more attributes

现在，可以从配置文件对象中执行 profile.group 。但是，如果要为配置文件对象提供 group 对象，您将如何做？那就是相关名称或反向关系出现的地方。

Now, from a profile object, you can do profile.group. But if you want the profile objects given the group object, How would you do that? Thats' where related name or the reverse relationship comes in.

Django，默认情况下为您提供默认的 related_name ，即ModelName（小写），后跟 set -在这种情况下，它是 profile_set ，所以 group.profile_set 。

Django, by defaults gives you a default related_name which is the ModelName (in lowercase) followed by _set - In this case, It would be profile_set, so group.profile_set.

不过，您可以通过在 ForeignKey related_name 来覆盖它c $ c>字段。

However, you can override it by specifying a related_name in the ForeignKey field.

class Profile(models.Model):
    group = models.ForeignKey(Group, related_name='profiles')
    #more attributes

现在，您可以访问外键了如下所示：

Now, you can access the foreign key as follows:

group.profiles.all()

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