Day 4 - 编写Model · Python 3零起点教程

有了ORM，我们就可以把Web App需要的3个表用`Model`表示出来： ~~~ import time, uuid from orm import Model, StringField, BooleanField, FloatField, TextField def next_id(): return '%015d%s000' % (int(time.time() * 1000), uuid.uuid4().hex) class User(Model): __table__ = 'users' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') email = StringField(ddl='varchar(50)') passwd = StringField(ddl='varchar(50)') admin = BooleanField() name = StringField(ddl='varchar(50)') image = StringField(ddl='varchar(500)') created_at = FloatField(default=time.time) class Blog(Model): __table__ = 'blogs' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') user_id = StringField(ddl='varchar(50)') user_name = StringField(ddl='varchar(50)') user_image = StringField(ddl='varchar(500)') name = StringField(ddl='varchar(50)') summary = StringField(ddl='varchar(200)') content = TextField() created_at = FloatField(default=time.time) class Comment(Model): __table__ = 'comments' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') blog_id = StringField(ddl='varchar(50)') user_id = StringField(ddl='varchar(50)') user_name = StringField(ddl='varchar(50)') user_image = StringField(ddl='varchar(500)') content = TextField() created_at = FloatField(default=time.time) ~~~ 在编写ORM时，给一个Field增加一个`default`参数可以让ORM自己填入缺省值，非常方便。并且，缺省值可以作为函数对象传入，在调用`save()`时自动计算。例如，主键`id`的缺省值是函数`next_id`，创建时间`created_at`的缺省值是函数`time.time`，可以自动设置当前日期和时间。日期和时间用`float`类型存储在数据库中，而不是`datetime`类型，这么做的好处是不必关心数据库的时区以及时区转换问题，排序非常简单，显示的时候，只需要做一个`float`到`str`的转换，也非常容易。 ### 初始化数据库表如果表的数量很少，可以手写创建表的SQL脚本： ~~~ -- schema.sql drop database if exists awesome; create database awesome; use awesome; grant select, insert, update, delete on awesome.* to 'www-data'@'localhost' identified by 'www-data'; create table users ( `id` varchar(50) not null, `email` varchar(50) not null, `passwd` varchar(50) not null, `admin` bool not null, `name` varchar(50) not null, `image` varchar(500) not null, `created_at` real not null, unique key `idx_email` (`email`), key `idx_created_at` (`created_at`), primary key (`id`) ) engine=innodb default charset=utf8; create table blogs ( `id` varchar(50) not null, `user_id` varchar(50) not null, `user_name` varchar(50) not null, `user_image` varchar(500) not null, `name` varchar(50) not null, `summary` varchar(200) not null, `content` mediumtext not null, `created_at` real not null, key `idx_created_at` (`created_at`), primary key (`id`) ) engine=innodb default charset=utf8; create table comments ( `id` varchar(50) not null, `blog_id` varchar(50) not null, `user_id` varchar(50) not null, `user_name` varchar(50) not null, `user_image` varchar(500) not null, `content` mediumtext not null, `created_at` real not null, key `idx_created_at` (`created_at`), primary key (`id`) ) engine=innodb default charset=utf8; ~~~ 如果表的数量很多，可以从`Model`对象直接通过脚本自动生成SQL脚本，使用更简单。把SQL脚本放到MySQL命令行里执行： ~~~ $ mysql -u root -p < schema.sql ~~~ 我们就完成了数据库表的初始化。 ### 编写数据访问代码接下来，就可以真正开始编写代码操作对象了。比如，对于`User`对象，我们就可以做如下操作： ~~~ import orm from models import User, Blog, Comment def test(): yield from orm.create_pool(user='www-data', password='www-data', database='awesome') u = User(name='Test', email='test@example.com', passwd='1234567890', image='about:blank') yield from u.save() for x in test(): pass ~~~ 可以在MySQL客户端命令行查询，看看数据是不是正常存储到MySQL里面了。 ### 参考源码 [day-04](https://github.com/michaelliao/awesome-python3-webapp/tree/day-04)