Add database application for chapter 5

demos/database/.flaskenv

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+FLASK_ENV=development

demos/database/app.py

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+# -*- coding: utf-8 -*-
+import os
+import sys
+
+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')
+
+app.config['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)
+
+
+# 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.cli.command()
+@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
+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):
+    id = db.Column(db.Integer, primary_key=True)
+    body = db.Column(db.Text)
+
+    # optional
+    def __repr__(self):
+        return '<Note %r>' % self.body
+
+
+@app.route('/')
+def index():
+    form = DeleteNoteForm()
+    notes = Note.query.all()
+    return render_template('index.html', notes=notes, form=form)
+
+
+@app.route('/new', methods=['GET', 'POST'])
+def new_note():
+    form = NewNoteForm()
+    if form.validate_on_submit():
+        body = form.body.data
+        note = Note(body=body)
+        db.session.add(note)
+        db.session.commit()
+        flash('Your note is saved.')
+        return redirect(url_for('index'))
+    return render_template('new_note.html', form=form)
+
+
+@app.route('/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.commit()
+        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)
+
+
+@app.route('/delete/<int:note_id>', methods=['POST'])
+def delete_note(note_id):
+    form = DeleteNoteForm()
+    if form.validate_on_submit():
+        note = Note.query.get(note_id)
+        db.session.delete(note)
+        db.session.commit()
+        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
+
+    def __repr__(self):
+        return '<Author %r>' % self.name
+
+
+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'))
+
+    def __repr__(self):
+        return '<Article %r>' % self.title
+
+
+# many to one
+class Citizen(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(70), unique=True)
+    city_id = db.Column(db.Integer, db.ForeignKey('city.id'))
+    city = db.relationship('City')  # scalar
+
+    def __repr__(self):
+        return '<Citizen %r>' % self.name
+
+
+class City(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(30), unique=True)
+
+    def __repr__(self):
+        return '<City %r>' % self.name
+
+
+# one to one
+class Country(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(30), unique=True)
+    capital = db.relationship('Capital', 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')  # scalar
+
+    def __repr__(self):
+        return '<Capital %r>' % self.name
+
+
+# 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
+
+
+# one to many + bidirectional relationship
+class Writer(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(64), unique=True)
+    books = db.relationship('Book', back_populates='writer')
+
+    def __repr__(self):
+        return '<Writer %r>' % self.name
+
+
+class Book(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    title = db.Column(db.String(50), index=True)
+    writer_id = db.Column(db.Integer, db.ForeignKey('writer.id'))
+    writer = db.relationship('Writer', back_populates='books')
+
+    def __repr__(self):
+        return '<Book %r>' % self.name
+
+
+# one to many + bidirectional relationship + use backref to declare bidirectional relationship
+class Singer(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(70), unique=True)
+    songs = db.relationship('Song', backref='singer')
+
+    def __repr__(self):
+        return '<Singer %r>' % self.name
+
+
+class Song(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(50), index=True)
+    singer_id = db.Column(db.Integer, db.ForeignKey('singer.id'))
+
+    def __repr__(self):
+        return '<Song %r>' % self.name
+
+
+# cascade
+class Post(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    title = db.Column(db.String(50))
+    body = db.Column(db.Text)
+    comments = db.relationship('Comment', back_populates='post', cascade='all, delete-orphan')  # collection
+
+
+class Comment(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    body = db.Column(db.Text)
+    post_id = db.Column(db.Integer, db.ForeignKey('post.id'))
+    post = db.relationship('Post', back_populates='comments')  # scalar
+
+
+# event listening
+class Draft(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    body = db.Column(db.Text)
+    edit_time = db.Column(db.Integer, default=0)
+
+
+@db.event.listens_for(Draft.body, 'set')
+def increment_edit_time(target, value, oldvalue, initiator):
+    if target.edit_time is not None:
+        target.edit_time += 1
+
+# same with:
+# @db.event.listens_for(Draft.body, 'set', named=True)
+# def increment_edit_time(**kwargs):
+#     if kwargs['target'].edit_time is not None:
+#         kwargs['target'].edit_time += 1

demos/database/static/styles.css

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+body {
+    margin: auto;
+    width: 750px;
+}
+
+nav ul {
+    list-style-type: none;
+    margin: 0;
+    padding: 0;
+    overflow: hidden;
+    background-color: #333;
+}
+
+nav li {
+    float: left;
+}
+
+nav li a {
+    display: block;
+    color: white;
+    text-align: center;
+    padding: 14px 16px;
+    text-decoration: none;
+}
+
+nav li a:hover {
+    background-color: #111;
+}
+
+main {
+    padding: 10px 20px;
+}
+
+footer {
+    font-size: 13px;
+    color: #888;
+    border-top: 1px solid #eee;
+    margin-top: 25px;
+    text-align: center;
+    padding: 20px;
+
+}
+
+.alert {
+  position: relative;
+  padding: 0.75rem 1.25rem;
+  margin-bottom: 1rem;
+  border: 1px solid transparent;
+  border-radius: 0.25rem;
+  color: #004085;
+  background-color: #cce5ff;
+  border-color: #b8daff;
+}
+
+.note p {
+    padding: 10px;
+    border-left: solid 2px #bbb;
+}
+
+.note form {
+    display: inline;
+}
+
+
+.btn {
+    font-family: Arial;
+    font-size: 14px;
+    padding: 5px 10px;
+    text-decoration: none;
+    border:none;
+    cursor: pointer;
+    background-color: white;
+    color: black;
+    border: 2px solid #555555;
+}
+
+.btn:hover {
+  text-decoration: none;
+  background-color: black;
+  color: white;
+  border: 2px solid black;
+}