Blogging on App Engine Interlude: Editing and listing

Posted by Nick Johnson | Filed under coding, app-engine, tech, bloggart

This is part of a series of articles on writing a blogging system on App Engine. An overview of what we're building is here.

A couple of things didn't quite make it into part 2 of the series: Listing and editing posts in the admin interface. This post is a short 'interlude' between the main posts in the series, and briefly covers the changes needed for those features.

Editing posts requires surprisingly little work, thanks to our use of the Django forms library. First, we write a decorator function that we can attach to methods that require an optional post ID, loading the relevant BlogPost object for us:

def with_post(fun):
  def decorate(self, post_id=None):
    post = None
    if post_id:
      post = BlogPost.get_by_id(int(post_id))
      if not post:
        self.error(404)
        return
    fun(self, post)
  return decorate

Then, we enhance the PostHandler to take an optional post ID argument, using the decorator we just defined. Here's the new get() method:

  @with_post
  def get(self, post):
    self.render_form(PostForm(instance=post))

If no post ID is supplied, post is None, and the form works as it used to. If a post ID is supplied, the post variable contains ...

Read more | Comments | 08 October, 2009

Blogging on App Engine, part 2: Basic blogging

Posted by Nick Johnson | Filed under coding, app-engine, tech, bloggart

This is the second in a series of articles on writing a blogging system on App Engine. An overview of what we're building is here.

In this post, we'll be handling the most basic part of blogging: Submitting new posts. For this, we're going to have to create our admin interface - which will involve a fair bit of boilerplate - as well as templates for both the admin interface and the blog posts themselves. But first, we need to make a slight change to the static serving code.

In order to publish new blog posts, we need to make sure we can generate a unique URL for the post, and for that we need a new method in the static serving interface. We'll call it 'add', and define it in static.py like so:

def add(path, body, content_type, **kwargs):
  def _tx():
    if StaticContent.get_by_key_name(path):
      return None
    return set(path, body, content_type, **kwargs)
  return db.run_in_transaction(_tx)

add() is a fairly straightforward transactional wrapper for set(), which first checks if a resource with the provided URL path already exists, and only creates it if it doesn't, returning None otherwise.

Next, we need to add routing ...

Read more | Comments | 07 October, 2009

Blogging on App Engine, part 1: Static serving

Posted by Nick Johnson | Filed under coding, app-engine, tech, bloggart

This is the first in a series of articles on writing a blogging system on App Engine. An overview of what we're building is here.

As promised, today we'll be covering the static serving component of our blog-to-be. First, though, is the naming issue. There were a lot of good names proposed by readers. Unfortunately, pretty much every one of them is taken on appspot.com. In the end, I settled on a name suggested to me out-of-band: 'bloggart'. My wife, who loves to draw, has kindly promised to draw me a picture of a boastful looking monster to act as a mascot.

Now down to business. Create a new app called 'bloggart-demo' (or whatever you wish, really), and put the following in its app.yaml file:

application: bloggart-demo
version: live
runtime: python
api_version: 1

handlers:
- url: /remote_api
  script: $PYTHON_LIB/google/appengine/ext/remote_api/handler.py
  login: admin

- url: /.*
  script: static.py

Note that we're including remote_api right away. Without any sort of admin interface at this stage, it's going to be our only way of creating some initial content to test things out with. As discussed in the introductory post, we're separating out the ...

Read more | Comments | 05 October, 2009

Win a Dell Netbook and $1000 of App Engine credit!

Posted by Nick Johnson | Filed under coding, app-engine, tech

Just a quick note: We recently announced a competition on the App Engine blog: Develop an App Engine app that uses Twilio, and you could win a Dell Netbook and $1000 of App Engine credit! Twilio is an excellent service that lets you write sophisticated telephony applications, entirely over HTTP.

You have until October 4th to enter. I really wish I could, but as part of the team, I'm disqualified. ;)

Read more | Comments | 05 October, 2009

Writing a blog system on App Engine

Posted by Nick Johnson | Filed under coding, app-engine, tech, bloggart

I'm going to spend the next few posts working through the process of writing a simple, robust and scalable blogging system for App Engine. This first post is going to be fairly dull, unfortunately, as it will serve to cover what our requirements and non-requirements are, and the general approach we're going to take to achieve those objectives. In other words: Lots of bullet points, and little to no code. Don't worry, it'll get more exciting soon.

First, let's outline what we (or at least, I) expect out of a blogging system:

  • Simple authoring. I personally don't want to juggle with WYSIWYG HTML editors in order to write blog posts - I prefer to enter markup directly. But at the same time, I don't intend to make all potential users conform to the same expectations - so we should be able to support rich text editors if they're desired.
  • Good isolation of code and markup. Users shouldn't have to understand the innards of our blogging software if all they want to do is change how the blog looks or is laid out.
  • RSS and Atom support. This should go without saying, these days ...

Read more | Comments | 02 October, 2009

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