Tutorial¶
In this tutorial, we will create a simple blog application. You can learn to cache with rc and Python here. In our blog application, anyone can add or update a post, view all posts.
Create Skeleton¶
For this simple web application, we choose to use Flask. Here is the basic skeleton:
# -*- coding: utf-8 -*-
import time
from flask import Flask
from flask import request, url_for, redirect, abort, render_template_string
from flask_sqlalchemy import SQLAlchemy
from rc import Cache
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
db = SQLAlchemy(app)
cache = Cache()
def init_db():
db.create_all()
if __name__ == '__main__':
init_db()
app.run()
Create Models¶
Let’s declare the models and create the database schema here:
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(100), nullable=False)
content = db.Column(db.Text, nullable=False)
created_ts = db.Column(db.Integer, nullable=False)
updated_ts = db.Column(db.Integer, nullable=False)
def __init__(self, title, content, created_ts, updated_ts):
self.title = title
self.content = content
self.created_ts = created_ts
self.updated_ts = updated_ts
def __repr__(self):
return '<Post %s>' % self.id
@staticmethod
def add(title, content):
current_ts = int(time.time())
post = Post(title, content, current_ts, current_ts)
db.session.add(post)
db.session.commit()
cache.invalidate(Post.get_by_id, post.id)
cache.invalidate(Post.get_all_ids)
@staticmethod
def update(post_id, title, content):
post = Post.query.get(post_id)
post.title = title
post.content = content
post.updated_ts = int(time.time())
db.session.commit()
cache.invalidate(Post.get_by_id, post.id)
@staticmethod
@cache.cache()
def get_all_ids():
posts = Post.query.all()
return [post.id for post in posts]
@staticmethod
@cache.cache()
def get_by_id(post_id):
post = Post.query.get(post_id)
return dict(id=post.id, title=post.title, content=post.content,
created_ts=post.created_ts, updated_ts=post.updated_ts)
View Functions¶
We will have four view functions here, they are used to add or update or view a single post, view all posts. The code explains itself:
@app.route('/add', methods=['POST'])
def add_post():
title = request.form['title']
content = request.form['content']
Post.add(title, content)
return redirect(url_for('show_all_posts'))
@app.route('/post/<int:post_id>')
def show_post(post_id):
post = Post.get_by_id(post_id)
if post is None:
abort(404)
return render_template_string(SHOW_POST_TEMPLATE, post=post)
@app.route('/post/<int:post_id>', methods=['POST'])
def edit_post(post_id):
post = Post.get_by_id(post_id)
if post is None:
abort(404)
title = request.form['title']
content = request.form['content']
Post.update(post_id, title, content)
return redirect(url_for('show_all_posts'))
@app.route('/')
def show_all_posts():
all_post_ids = Post.get_all_ids()
all_posts = []
with cache.batch_mode():
for post_id in all_post_ids:
all_posts.append(Post.get_by_id(post_id))
all_posts = [p.value for p in all_posts]
return render_template_string(ALL_POSTS_TEMPLATE, all_posts=all_posts)
Add The Templates¶
The template for showing all posts is here.
<!DOCTYPE html>
<html>
<head>
<title>Blog</title>
</head>
<body>
<h1>Blog</h1>
<form action="{{ url_for('add_post') }}" method=post>
<dl>
<dt>Title:
<dd><input type=text size=50 name=title>
<dt>Content:
<dd><textarea name=content rows=5 cols=40></textarea>
<dd><input type=submit value=Post>
</dl>
</form>
<ul>
{% for post in all_posts %}
<li>
<a href="{{ url_for('show_post', post_id=post.id) }}">
{{ post.title }}
</a>
</li>
{% endfor %}
</ul>
</body>
</html>
The template for showing one post is here.
<!DOCTYPE html>
<html>
<head>
<title>{{ post.title }}</title>
</head>
<body>
<h1>{{ post.title }}</h1>
<p>{{ post.content }}</p>
<form action="{{ url_for('edit_post', post_id=post.id) }}" method=post>
<dl>
<dt>Title:
<dd><input type=text size=50 name=title>
<dt>Content:
<dd><textarea name=content rows=5 cols=40></textarea>
<dd><input type=submit value=Update>
</dl>
</form>
</body>
</html>
If you want the full source code check out the tutorial source.
