Chicken Scratches

Get it? It's a fantasy sports draft application, but it's spelled draught. Like draught beer. I like to watch football with a beer or two, and everyone loves a good pun. So there you go.

In my fantasy football and baseball leagues, we wanted to do a live draft, but we have players who live on both coasts, who work varying schedules, and some of whom have kids. Plus one of our rules is we allow keeping two to four players from year to year, to give some continuity.

Because of those two factors, it's impossible for us to use Yahoo!'s live draft or autodraft. So what does your trusty software engineer do? He codes up his own draft application, of course!

Welcome to the third part in my series of posts about creating a Facebook application. I am using Django as my web development framework, and this post will focus on some of the backend techniques I have worked out to make this work easier. This is not a tutorial, but a set of tools that I have developed. This is a long post, with a lot of source code; I hope you find at least some of it useful.

Keep in mind as you read this that the Facebook platform is still very new, and likely to change. In fact, if you're a FB user, you are probably aware they recently completed a major transition to a new profile design. This included many changes behind the scenes for developers, some of which are still playing out. I recommend keeping up with the Facebook Platform Developer Forum and the Facebook Developer Blog.

Also, I will assume you have already read the API Documentation and the documentation for PyFacebook, and that you know how to create a web app using Django. If not, you will want to start there.

Welcome to the second part in my series of posts about creating a Facebook application. I am using Django as my web development framework, but this post doesn't have much to do with Django, since it deals with the front end. In particular, it talks about how to write JavaScript that can work both in and out of Facebook.

As I mentioned last time, Facebook lets developers use a subset of JavaScript, which they call FBJS. The FBJS is transformed on the fly into JavaScript as the page is loaded. All variables and functions you define or reference are prepended with a string like "a123456789_", including calls to document.getElementById and setTimer and the like. This is done in order to restrict what you can do with DOM elements, to avoid cross-site-scripting attacks and unwanted user-hostile behavior. FBJS is fairly well documented, so if you plan to do some Facebook JavaScript development, you should start there.

The biggest restriction that FBJS imposes is that you can no longer access the attributes of DOM elements directly, but must go through an abstraction API consisting of a series of setters and getters. For example, instead of saying something like imageEl.src = myImageUrl, you instead need to call imageEl.setSrc(myImageUrl).