django抽象模型与常规遗传 [英] django abstract models versus regular inheritance

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问题描述

除了语法,使用django抽象模型和使用简单的Python继承与django模型有什么区别?优点和缺点?



更新:我认为我的问题被误解,我收到了一个抽象模型和继承自django.db.models的类之间的区别的回应。模型。 我实际上想知道从django抽象类(Meta:abstract = True)继承的模型类与继承自object(而不是models.Model)的普通Python类之间的区别。 / strong>



这是一个例子:

  class User对象):
first_name = models.CharField(..

def get_username(self):
return self.username

class User模型):
first_name = models.CharField(...

def get_username(self):
return self.username

class Meta:
abstract = True

class员工(用户):
title = models.CharField(...


解决方案


我真的想知道
从django抽象继承的模型类之间的区别class(Meta:abstract = True)和一个
纯Python类,继承自say,'object'(和n
models.Model)。


Django将只生成 models的子类的表。模型,所以前者...

  class User(models.Model):
first_name = models.CharField(max_length = 255)

def get_username(self):
return self.username

class Meta:
abstract = True

class员工(用户):
title = models.CharField(max_length = 255)

...将导致生成一个表,沿...的行...

  CREATE TABLE myapp_employee 

id INT NOT NULL AUTO_INCREMENT,
first_name VARCHAR(255)NOT NULL,
title VARCHAR(255)NOT NULL,
PRIMARY KEY )
);

...而后者...



$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $

$ b $ get $ return self.username

class Employee(User):
title = models.CharField(max_length = 255)

...不会导致生成任何表。



您可以使用多重继承来执行此操作...

  class User(object):
first_name = models.CharField(max_length = 255)

def get_username(self):
return self.username

class Employee(User,models.Model):
title = models.CharField(max_length = 255)

...将创建一个表,但它将忽略 User 类中定义的字段,因此最终会出现如下表格...

  CREATE TABLE myapp_employee 

id INT NOT NULL AUTO_INCREMENT,
title VARCHAR(255)NOT NULL,
PRIMARY KEY(id)
);


Besides the syntax, what's the difference between using a django abstract model and using plain Python inheritance with django models? Pros and cons?

UPDATE: I think my question was misunderstood and I received responses for the difference between an abstract model and a class that inherits from django.db.models.Model. I actually want to know the difference between a model class that inherits from a django abstract class (Meta: abstract = True) and a plain Python class that inherits from say, 'object' (and not models.Model).

Here is an example:

class User(object):
   first_name = models.CharField(..

   def get_username(self):
       return self.username

class User(models.Model):
   first_name = models.CharField(...

   def get_username(self):
       return self.username

   class Meta:
       abstract = True

class Employee(User):
   title = models.CharField(...

解决方案

I actually want to know the difference between a model class that inherits from a django abstract class (Meta: abstract = True) and a plain Python class that inherits from say, 'object' (and not models.Model).

Django will only generate tables for subclasses of models.Model, so the former...

class User(models.Model):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

   class Meta:
       abstract = True

class Employee(User):
   title = models.CharField(max_length=255)

...will cause a single table to be generated, along the lines of...

CREATE TABLE myapp_employee
(
    id         INT          NOT NULL AUTO_INCREMENT,
    first_name VARCHAR(255) NOT NULL,
    title      VARCHAR(255) NOT NULL,
    PRIMARY KEY (id)
);

...whereas the latter...

class User(object):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

class Employee(User):
   title = models.CharField(max_length=255)

...won't cause any tables to be generated.

You could use multiple inheritance to do something like this...

class User(object):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

class Employee(User, models.Model):
   title = models.CharField(max_length=255)

...which would create a table, but it will ignore the fields defined in the User class, so you'll end up with a table like this...

CREATE TABLE myapp_employee
(
    id         INT          NOT NULL AUTO_INCREMENT,
    title      VARCHAR(255) NOT NULL,
    PRIMARY KEY (id)
);

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