Sat 29 Nov 2008
Before October I had never written Objective-C. Also I haven’t written a huge amount of C over the years, so it was quite interesting to try this out. Every time I’d looked at Objective-C so far I’d always thought it looked a bit odd with the crazy square brackets and the strange method names. In fact here’s a sample from iFreeThePostcode, this is a basic function that receives a new location, stores it for later use and passes it on to another object too:
At Liverpool GeekUp in September Dave Verwer gave a talk about iPhone development. It was quite a basic talk but afterwards I was talking to Dave and he suggested I tried reading “Cocoa Programming for Mac OS X” by Aaron Hillegass. I also got the same recommendation from Colm McMullan, creator of Yofe, so I decided it must be worth reading. I read the whole book while on holiday and the following week set about writing my first app. If you’re planning to start writing iPhone apps I’d definitely recommend this book, if you feel like using the Amazon link on the right then I’ll even make money when you buy it!
My first app was actually not iFreeThePostcode but was in fact a routing app. I’ve taken the Gosmore routing library from Open Street Map, the same library that’s used for www.yournavigation.org, and have ported it to Objective-C. It actually works really well on the iPhone and can give speedy routes, though so far I’ve had to limit it to small datasets. Hopefully that’s a limitation I’ll be able to work around. It was when I was ready to add the GPS support to this app that I decided it would probably be easier to try with a simpler app first, and from there iFreeThePostcode was born.
iFreeThePostcode is a ridiculously simple app. The aim of it is to allow you to submit postcodes to the Free the Postcode project. This is a project to create a public domain postcode database in the UK, a much cheaper option than the existing database which costs a lot when bought from the Royal Mail. When you start up the app it shows you a few text boxes and your current latitude and longitude (or “Loading…” initially). Your horizontal accuracy is also shown and will start off in red. When your accuracy goes below 100m it will turn green and you will be able to submit your postcode. You have to enter the postcode as two separate parts, i.e. “EC4A2DY” would be entered as “EC4A” and “2DY”. You also need to enter a valid email address, this is to stop spammers sending useless data and to allow some tracking of who has submitted what postcodes. If someone is found to be submitting copyrighted data, their submissions could therefore be removed. Once you click submit you should get a success or failure message. Failures can be caused by not entering a valid email address or postcode, or by problems communicating with the server. If your submission succeeds you will receive an email containing a special link. Click on the link and your submission should show up in the current public domain list of UK postcodes the next day!
I really hope that by making submissions to Free the Postcode really easy that a lot more postcodes will be submitted. Obviously this is only useful to iPhone users but by most accounts there’s a lot of us out there, also this might inspire someone else to write a similar app for Android, Symbian or Windows Mobile phones which would take the idea to even more people.
Though there’s not a lot of code in this app I’ve decided to make it open source. Hopefully it will help someone who’s looking to get started with iPhone development. A few of the more interesting parts would be the code for handling the current location and the code for submitting the postcode to the website. To download the source code head over to the iFreeThePostcode page. The code that I’ll make available initially is basically the same as the code that is live except that I’ve gone through it to add some more comments. There are a few bugs that I’m aware of though and I’ll work on them soon and release a new version to the app store as soon as they’re done. For more information keep an eye on that page.