在 Django - 模型继承 - 它是否允许您覆盖父模型的属性? [英] In Django - Model Inheritance - Does it allow you to override a parent model's attribute?

问题描述

我希望这样做:

class Place(models.Model):
   name = models.CharField(max_length=20)
   rating = models.DecimalField()

class LongNamedRestaurant(Place):  # Subclassing `Place`.
   name = models.CharField(max_length=255)  # Notice, I'm overriding `Place.name` to give it a longer length.
   food_type = models.CharField(max_length=25)

这是我想使用的版本(尽管我愿意接受任何建议):http://docs.djangoproject.com/en/dev/topics/数据库/模型/#id7

This is the version I would like to use (although I'm open to any suggestion): http://docs.djangoproject.com/en/dev/topics/db/models/#id7

Django 支持这个吗?如果没有，有没有办法达到类似的结果?

Is this supported in Django? If not, is there a way to achieve similar results?

推荐答案

更新的答案:正如人们在评论中指出的那样，原始答案没有正确回答问题.事实上，只有 LongNamedRestaurant 模型在数据库中创建，Place 没有.

Updated answer: as people noted in comments, the original answer wasn't properly answering the question. Indeed, only the LongNamedRestaurant model was created in database, Place was not.

一个解决方案是创建一个代表地方"的抽象模型，例如.AbstractPlace，并继承它:

A solution is to create an abstract model representing a "Place", eg. AbstractPlace, and inherit from it:

class AbstractPlace(models.Model):
    name = models.CharField(max_length=20)
    rating = models.DecimalField()

    class Meta:
        abstract = True

class Place(AbstractPlace):
    pass

class LongNamedRestaurant(AbstractPlace):
    name = models.CharField(max_length=255)
    food_type = models.CharField(max_length=25)

另请阅读@Mark answer，他很好地解释了为什么您不能更改从非-抽象类.

Please also read @Mark answer, he gives a great explanation why you can't change attributes inherited from a non-abstract class.

(请注意，这仅在 Django 1.10 之后才有可能:在 Django 1.10 之前，无法修改从抽象类继承的属性.)

(Note this is only possible since Django 1.10: before Django 1.10, modifying an attribute inherited from an abstract class wasn't possible.)

自 Django 1.10 它是可能！你只需要按照你的要求去做:

Original answer

Since Django 1.10 it's possible! You just have to do what you asked for:

class Place(models.Model):
    name = models.CharField(max_length=20)
    rating = models.DecimalField()

    class Meta:
        abstract = True

class LongNamedRestaurant(Place):  # Subclassing `Place`.
    name = models.CharField(max_length=255)  # Notice, I'm overriding `Place.name` to give it a longer length.
    food_type = models.CharField(max_length=25)

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