ForeignKey（User，unique = True）和OneToOneField之间的区别 [英] Difference between ForeignKey(User, unique=True) and OneToOneField

问题描述

Django中的 models.ForeignKey（Modelname，unique = True）和 models.OneToOneField 之间有什么区别？

我应该在哪里使用 models.OneToOneField 和 models.ForeignKey（Modelname，unique =真的）？

解决方案

A OneToOneField 非常类似于 ForeignKey 与 unique = True 。除非您正在执行多个表继承，否则您必须使用 OneToOneField ，唯一真正的区别是访问相关对象的api。

在 Django docs 中说：

从概念上讲，这类似于 ForeignKey 与 unique = True ，但关系的反向一方将直接返回单个对象。

让我们用一个例子来说明这是什么意思。考虑两个模型， Person 和地址。我们假设每个人都有一个唯一的地址。

  class Person（models.Model）：
 name = models .CharField（max_length = 50）
 address = models.ForeignKey（'Address'，unique = True）
 
 class地址（models.Model）：
 street = models.CharField （max_length = 50）
  

如果您从一个人开始，您可以轻松访问该地址： p>

  address = person.address 
  

但是，如果您从地址开始，您必须通过 person_set 管理员来获取该人。

  person = address.person_set.get（）＃可能会提高Person.DoesNotExist 
  

现在我们用 OneToOneField 替换 ForeignKey 。

  class Person（models.Model）：
 name = models.CharField（max_length = 50）
 address = models.OneToOneField（'地址'）
 
类地址（模型s.Model）：
 street = models.CharField（max_length = 50）
  

如果你从一个人开始，您可以以相同的方式访问地址：

  address = person.address 
  

现在，我们可以更轻松地从地址访问该人。

  person = address.person＃可以提高Person.DoesNotExist 
  




What is different between models.ForeignKey(Modelname, unique=True) and models.OneToOneField in Django?

Where should I use models.OneToOneField and models.ForeignKey(Modelname, unique=True)?

解决方案

A OneToOneField is very similar to a ForeignKey with unique=True. Unless you are doing multiple table inheritance, in which case you have to use OneToOneField, the only real difference is the api for accessing related objects.

In the Django docs it says:

Conceptually, this is similar to a ForeignKey with unique=True, but the "reverse" side of the relation will directly return a single object.

Let's show what that means with an example. Consider two models, Person and Address. We'll assume each person has a unique address.

class Person(models.Model):
    name = models.CharField(max_length=50)
    address = models.ForeignKey('Address', unique=True)

class Address(models.Model):
    street = models.CharField(max_length=50)

If you start with a person, you can access the address easily:

address = person.address

However if you start with an address, you have to go via the person_set manager to get the person.

person = address.person_set.get() # may raise Person.DoesNotExist

Now let's replace the ForeignKey with a OneToOneField.

class Person(models.Model):
    name = models.CharField(max_length=50)
    address = models.OneToOneField('Address')

class Address(models.Model):
    street = models.CharField(max_length=50)

If you start with a person, you can access the address in the same way:

address = person.address

And now, we can access the person from the address more easily.

person = address.person # may raise Person.DoesNotExist

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