Model Class & Database

Model 类 与 数据库 的对应关系

Model 结构

• 只有 Fields 是必须要的

from django.db import models

class Person(models.Model):

    # Fields
    first_name = models.CharField(max_length=64)
    last_name = models.CharField(max_length=64)
    age = models.IntegerField()

    # MetaData
    class Meta:
        ordering = ["-age"]
        verbose_name_plural = "people"

    # Model methods
    @property
    def full_name(self):
        "Returns the person's full name."
        return '%s %s' % (self.first_name, self.last_name)

    def __str__(self):
        return self.full_name()
    
    # Override predefined model methods
    def save(self, *args, **kwargs):
        do_something()
        super().save(*args, **kwargs)  # Call the "real" save() method.
        do_something_else()

Fields

Fields

Field Types

• model field reference
• Writing custom model fields

Field Options

• model field reference

项的选项分为：

• 公共：common model field option reference

• 私有

# 公共选项

CHOICES = [
    ('store value', 'display value')
]

# 选项 = 默认值
null = False
blank = False
default = 
help_text = 
primary = 
unique = 
verbose_name = # 也是第一个位置参数
choices = CHOICES # display value : .get_<field_name>_display()

Metadata

• model option reference

# metadata 用于定义关于整个表的附加信息
ordering  # 排序依据
db_table  # 表名
verbose_name  # 用于显示的 单数名称
verbose_name_plural  # 用于显示的 复数名称，默认是直接 +s

Model Methods

• Model methods

定义一个作用于数据库中的一行(record)的函数

通常需要定义：def __str__(self)
可能需要重载预定义的方法：save(), delete()

Using Models

# project/settings.py
INSTALLED_APP = [
    # ....
    'myapp',
    # ....
]

$ python manage.py makemigrations myapp
$ python manage.py migrate

Databse-access API

Making queries