LastEditors: huangjy
LastEditTime: 2020-11-22 10:02:18
Description: models api 学习和使用
'''
from boards.models import Board
#创建对象
board = Board(name='java', description='java is good language')
#保存对象
board.save()
#访问字段的值
board.id
board.name
board.description
#更新字段
board.description = "This is effective java"
board.description
#每个Django模型都带有一个特殊的属性; 我们称之为模型管理器(Model Manager) 可通过objects 访问
#通过objects 创建新对象
board = Board.objects.create(name="Python",
description="General discussion about Python")
#>>> Board.objects.all()
# <QuerySet [<Board: Board object (1)>, <Board: Board object (2)>, <Board: Board object (3)>]>
#未实现 Board 的__str__ 方法。__str__方法是对象的字符串表示形式
# 定义之后展示
#<QuerySet [<Board: 板块id：1, 板块名称：Django>, <Board: 板块id：2, 板块名称：java>, <Board: 板块id：3, 板块名称：Python>]>
#获取指定id的内容
Board.objects.get(id=3)
Board.objects.get(name='django')
#apply the migration we generated to the database
python manage.py migrate
#You can start a Python shell with our project loaded using the manage.py utility
python manage.py shell
#importing the Board class
from boards.models import Board
#create a new board object, we can do the following
board = Board(name='Django', description='This is a board about Django.')
#To persist this object in the database, we have to call the save method
board.save()
#You can access the rest of the fields as Python attributes
board.name
#To update a value we could do
board.description = 'Django discussion board.'
board.save()
#We can use the objects to list all existing boards in the database
Board.objects.all()
#exit the interactive console
exit()
#The __str__ method is a String representation of an object. We can use the board name to represent it.
class Board(models.Model):
name = models.CharField(max_length=30, unique=True)
description = models.CharField(max_length=100)
def __str__(self):
return self.name
