# Day 4 - 編寫Model 有了ORM，我們就可以把Web App需要的3個表用`Model`表示出來： ``` import time, uuid from transwarp.db import next_id from transwarp.orm import Model, StringField, BooleanField, FloatField, TextField class User(Model): __table__ = 'users' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') email = StringField(updatable=False, ddl='varchar(50)') password = StringField(ddl='varchar(50)') admin = BooleanField() name = StringField(ddl='varchar(50)') image = StringField(ddl='varchar(500)') created_at = FloatField(updatable=False, default=time.time) class Blog(Model): __table__ = 'blogs' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') user_id = StringField(updatable=False, 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(updatable=False, default=time.time) class Comment(Model): __table__ = 'comments' id = StringField(primary_key=True, default=next_id, ddl='varchar(50)') blog_id = StringField(updatable=False, ddl='varchar(50)') user_id = StringField(updatable=False, ddl='varchar(50)') user_name = StringField(ddl='varchar(50)') user_image = StringField(ddl='varchar(500)') content = TextField() created_at = FloatField(updatable=False, default=time.time) ``` 在編寫ORM時，給一個Field增加一個`default`參數可以讓ORM自己填入缺省值，非常方便。并且，缺省值可以作為函數對象傳入，在調用`insert()`時自動計算。 例如，主鍵`id`的缺省值是函數`next_id`，創建時間`created_at`的缺省值是函數`time.time`，可以自動設置當前日期和時間。 日期和時間用`float`類型存儲在數據庫中，而不是`datetime`類型，這么做的好處是不必關心數據庫的時區以及時區轉換問題，排序非常簡單，顯示的時候，只需要做一個`float`到`str`的轉換，也非常容易。 ### 初始化數據庫表 如果表的數量很少，可以手寫創建表的SQL腳本： ``` -- 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, `password` 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; ``` 如果表的數量很多，可以從`Model`對象直接通過腳本自動生成SQL腳本，使用更簡單。 把SQL腳本放到MySQL命令行里執行： ``` $ mysql -u root -p < schema.sql ``` 我們就完成了數據庫表的初始化。 ### 編寫數據訪問代碼 接下來，就可以真正開始編寫代碼操作對象了。比如，對于`User`對象，我們就可以做如下操作： ``` # test_db.py from models import User, Blog, Comment from transwarp import db db.create_engine(user='www-data', password='www-data', database='awesome') u = User(name='Test', email='test@example.com', password='1234567890', image='about:blank') u.insert() print 'new user id:', u.id u1 = User.find_first('where email=?', 'test@example.com') print 'find user\'s name:', u1.name u1.delete() u2 = User.find_first('where email=?', 'test@example.com') print 'find user:', u2 ``` 可以在MySQL客戶端命令行查詢，看看數據是不是正常存儲到MySQL里面了。