《FlaskWeb 开发实战：⼊门、进阶与原理解析》-李辉笔记代码学习和注释（第
五章-数据库）
⼀、ORM
ORM⽤类来定义表，类的实例化代表了表的⼀整⾏，那么整个表就是类的实例化的LIST.
⼆、在表单中实现增删改查代码样例
增
删（⾥⾯包括了⽤主键查表的⾏）
改（直接覆盖掉就⾏了）
查@ute('/new', methods =['GET', 'POST'])def new_note ():#是⼀个⽐较典范的程序 form = NewNoteForm () if form .validate_on_submit (): body = form .body .data note = Note (body =body ) db .session .add (note ) db .session mit () flash ('Your note is saved.') return redirect (url_for ('index')) return render_template ('new_note.html', form =form )
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ute('/delete/<int:note_id>', methods =['POST'])def delete_note (note_id ): form = DeleteNoteForm () if form .validate_on_submit (): note = Note .query .get (note_id )#通过id 先到 db .session .delete (note )#然后直接删除掉 db .session mit () flash ('Your note is deleted.') else : abort (400) return redirect (url_for ('index'))
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数据库学习入门书籍10
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ute('/edit/<int:note_id>', methods =['GET', 'POST'])def edit_note (note_id ): form = EditNoteForm () note = Note .query .get (note_id ) if form .validate_on_submit (): note .body = form .body .data db .session mit () flash ('Your note is updated.') return redirect (url_for ('index')) form .body .data = note .body # preset form input's value return render_template ('edit_note.html', form =form )
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三、表关系
⼀对多
⼀对⼀
多对多note = Note .query .get (note_id )#查⼀⾏notes = Note .query .all ()#查全部
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3# one to many class Author (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (20), unique =True ) phone = db .Column (db .String (20)) articles = db .relationship ('Article') # collection ，这是⼀个集合关系属性，⾥⾯包含了作者的所有⽂章 def __repr__(self ): return '<Author %r>' % self .name #最后有两种⽅法来建⽴：#第⼀种是“多”这⼀端，直接给外键赋值#第⼆种是“⼀”这⼀端，将关系属性赋值给实际对象class Article (db .Model ): id = db .Column (db .Integer , primary_key =True ) title = db .Column (db .String (50), index =True ) body = db .Column (db .Text ) author_id = db .Column (db .Integer , db .ForeignKey ('author.id'))#⽤外键实现⼀对多的关系 def __repr__(self ): return '<Article %r>' % self .title 1
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# one to one #⼀对⼀就是⼀种特殊的⼀对多，只不过那个list ⾥的元素变成⼀个了⽽已class Country (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (30), unique =True ) capital = db .relationship ('Capital', back_populates ='country', uselist =False ) # collection -> scalar def __repr__(self ): return '<Country %r>' % self .name class Capital (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (30), unique =True ) country_id = db .Column (db .Integer , db .ForeignKey ('country.id')) country = db .relationship ('Country', back_populates ='capital') # scalar def __repr__(self ): return '<Capital %r>' % self .name
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借助关联表作为跳板，⼀⽅先对关联表进⾏检索，然后到对应的另⼀⽅信息。
三、总代码及注释# many to many with association table association_table = db .Table ('association', db .Column ('student_id', db .Integer , db .ForeignKey ('student.id')), db .Column ('teacher_id', db .Integer , db .ForeignKey ('teacher.id')) )class Student (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (70), unique =True ) grade = db .Column (db .String (20)) teachers = db .relationship ('Teacher',
secondary =association_table , back_populates ='students') # collection def __repr__(self ): return '<Student %r>' % self .name class Teacher (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (70), unique =True ) office = db .Column (db .String (20)) students = db .relationship ('Student', secondary =association_table , back_populates ='teachers') # collection def __repr__(self ): return '<Teacher %r>' % self .name
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31import os import sys import click
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import click from flask import Flask from flask import redirect , url_for , abort , render_template , flash from flask_sqlalchemy import SQLAlchemy from flask_wtf import FlaskForm from wtforms import SubmitField , TextAreaField from wtforms .validators import DataRequired # SQLite URI compatible WIN = sys .platform .startswith ('win')if WIN : prefix = 'sqlite:///'else : prefix = 'sqlite:'app = Flask (__name__)app .jinja_env .trim_blocks = True app .jinja_env .lstrip_blocks = True app .config ['SECRET_KEY'] = os .getenv ('SECRET_KEY', 'secret string')#配置数据库URI app .conf
ig ['SQLALCHEMY_DATABASE_URI'] = os .getenv ('DATABASE_URL', prefix + os .path .join (app .root_path , 'data.db'))app .config ['SQLALCHEMY_TRACK_MODIFICATIONS'] = False db = SQLAlchemy (app ) #实例化⼀个SQLAlchemy ，命名为db # handlers @app.shell_context_processor def make_shell_context (): return dict (db =db , Note =Note , Author =Author , Article =Article , Writer =Writer , Book =Book , Singer =Singer , Song =Song , Citizen =Citizen , City =City , Capital =Capital , Country =Country , Teacher =Teacher , Student =Student , Post =Post , Comment =Comment , Draft =Draft )@app.climand()@click.option('--drop', is_flag =True , help='Create after drop.')def initdb (drop ): """Initialize the database.""" if drop : db .drop_all () db .create_all () click .echo ('Initialized database.')# Forms #创建三个表单，分别⽤于填写新笔记、编辑笔记和删除笔记class NewNoteForm (FlaskForm ): body = TextAreaField ('Body', validators =[DataRequired ()]) submit = SubmitField ('Save')class EditNoteForm (FlaskForm ): body = TextAreaField ('Body', validators =[DataRequired ()]) submit = SubmitField ('Update')class DeleteNoteForm (FlaskForm ): submit = SubmitField ('Delete')# Models class Note (db .Model ): #定义了⼀个Note 类，即后⾯要实例化的笔记本的⾏，这⾥包含⼀个id 作为主键，还有⼀个⽂本内容 id = db .Column (db .Integer , primary_key =True ) body = db .Column (db .Text )
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# optional def __repr__(self ): return '<Note %r>' % self .body @ute('/')def index (): form = DeleteNoteForm () notes = Note .query .all () return render_template ('index.html', notes =notes , form =form )@ute('/new', methods =['GET', 'POST'])def new_note ():#是⼀个⽐较典范的程序 form = NewNoteForm () if form .validate_on_submit (): body = form .body .data note = Note (body =body ) db .session .add (note ) db .session mit () flash ('Your note is saved.') return redirect (url_for ('index')) return render_template ('new_note.html', form =form )@ute('/edit/<int:note_id>', methods =['GET', 'POST'])def edit_note (note_id ): form = EditNoteForm () note = Note .query .get (note_id ) if form .validate_on_submit (): note .body = form .body .data db .session mit () flash ('Your note is updated.') return redirect (url_for ('index')) form .body .data = note .body # preset form input's value return render_template ('edit_note.html', form =form )@ute('/delete/<int:note_id>', methods =['POST'])def delete_note (note_id ): form = DeleteNoteForm () if form .validate_on_submit (): note = Note .query .get (note_id )#通过id 先到 db .session .delete (note )#然后直接删除掉 db .session mit () flash ('Your note is deleted.') else : abort (400) return redirect (url_for ('index'))# one to many class Author (db .Model ): id = db .Column (db .Integer , primary_key =True ) name = db .Column (db .String (20), unique =True ) phone = db .Column (db .String (20)) articles = db .relationship ('Article') # collection ，这是⼀个集合关系属性，⾥⾯包含了
作者的所有⽂章 def __repr__(self ): return '<Author %r>' % self .name #最后有两种⽅法来建⽴：#第⼀种是“多”这⼀端，直接给外键赋值#第⼆种是“⼀”这⼀端，将关系属性赋值给实际对象class Article (db .Model ):707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135
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