related_name的作用是什么? [英] What does related_name do?

问题描述

在有关 related_name 的Django文档中，其内容如下:

In the Django documentation about related_name it says the following:

用于从相关对象到此对象的关系的名称.也是 related_query_name 的默认值(用于目标模型中反向过滤器名称的名称).有关完整的解释和示例，请参见相关的对象文档.注意，在抽象模型上定义关系时必须设置此值.并且当您这样做时，可以使用一些特殊的语法.

The name to use for the relation from the related object back to this one. It’s also the default value for related_query_name (the name to use for the reverse filter name from the target model). See the related objects documentation for a full explanation and example. Note that you must set this value when defining relations on abstract models; and when you do so some special syntax is available.

如果您不希望Django不要创建向后关系，请将related_name设置为'+'或以'+'结尾.

If you’d prefer Django not to create a backwards relation, set related_name to '+' or end it with '+'.

我不清楚.如果有人能再解释一下，那对我会有很大帮助.

I didn't understand it clearly. If somebody would please explain it a bit more, it would help me a lot.

推荐答案

创建外键时，您要将两个模型链接在一起.带有 ForeignKey()字段的模型使用字段名称来查找其他模型.还会在链接模型中隐式添加一个成员，以回溯此成员.

When you create a foreign key, you are linking two models together. The model with the ForeignKey() field uses the field name to look up the other model. It also implicitly adds a member to the linked model referring back to this one.

class Post(models.Model):
    # ... fields ...

class Comment(models.Model):
    # ... fields ...
    post = models.ForeignKey(Post, related_name=???)

这里有三种可能的情况:

There are three possible scenarios here:

如果您未指定名称，django将默认为您创建一个名称.

If you don't specify a name, django will create one by default for you.

some_post = Post.objects.get(id=12345)
comments = some_post.comment_set.all()

默认名称是关系的名称+ _set .

The default name is the relation's name + _set.

通常，您需要指定一些使其更自然的东西.例如， related_name ="comments" .

Usually you want to specify something to make it more natural. For example, related_name="comments".

some_post = Post.objects.get(id=12345)
comments = some_post.comments.all()

3.防止创建反向引用

有时您不想添加对外部模型的引用，因此请使用 related_name ="+" 来创建它.

some_post = Post.objects.get(id=12345)
comments = some_post.comment_set.all() # <-- error, no way to access directly

---

related_query_name 基本上是相同的想法，但是在查询集上使用 filter()时:

---

related_query_name is basically the same idea, but when using filter() on a queryset:

posts_by_user = Post.objects.filter(comments__user__id=123)

但是，老实说，因为默认使用 related_name 值，所以我从未使用过它.

But to be honest I've never used this since the related_name value is used by default.

这篇关于related_name的作用是什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！