This talk (based on a previous blog post here) goes into some detail about how I use HTTP, JSON and other web-oriented tech in my iPhone work.

I’m a web developer at heart, and a scripting language user by preference. Coding for the iPhone doesn’t feel as fluid in text handling or HTTP access as the environments I’m used to. Fortunately I’ve been able to find some fantastic open-source libraries and wrappers that make up the difference. Here are my favourites so far:

GTMHTTPFetcher from Google Toolbox for Mac

The iPhone’s native HTTP handling is capable, but low-level and verbose. Rather than handling the many callbacks, NSData objects and options I prefer this wrapper. It has a ton of convenience methods allowing you to specify POST data and basic auth, follow redirects automatically, keep cookies over a session, set headers, and have two simple callbacks for success and error handling. In many ways it’s comparable to jQuery’s $.ajax() one-hit function.

JSON framework

Having got some data over HTTP from a web API, chances are that it’s available in JSON format. This simple framework extends NSString with a JSONValue method to convert any legal JSON string to nested NSDictionaries and NSArrays. To go the other way, dictionaries and arrays gain a JSONRepresentation method.

libxml2 wrappers for XPath over XML and HTML

Perhaps your web API returns XML, or perhaps you’re getting your data by screenscraping HTML. Did you know that the iPhone ships with libxml2, which has high-performance XML and HTML parsing and a high-quality XPath implementation? Don’t struggle with Cocoa’s NSXMLParser or get bogged down in the complex libxml2 docs; use these two simple wrapper functions, PerformXMLXPathQuery and PerformHTMLXPathQuery, to pull out the structured data you need in a Cocoa-friendly representation.

RegexKitLite for regular expressions

Where would scripting be without regular expressions? Luckily they’re available on the iPhone, but buried deep within the ICU libraries. RegexKitLite extends NSString with core regex string handling, including ’split’ (known as componentsSeparatedByRegex) and a search-and-replace operator (stringByReplacingOccurrencesOfRegex and replaceOccurrencesOfRegex).

FMDB, an Objective C wrapper for sqlite

Every scripting language has convenient database driver wrappers. I was very happy to find that sqlite is available on the iPhone, but unfortunately its interface is all bare-metal C. The simplest wrapper I’ve found so far is FMDB. Apparently somewhat inspired by JDBC, it gives you connection and resultset objects, along with one-liner convenience functions allowing code like [db intForQuery:@"SELECT COUNT(*) FROM things"].

And there’s more…

I’ve used all of the above in a real project, but I’ve got yet more things to explore on my todo list. These include Matt Gemmell’s web-style templating framework MGTemplateEngine, ActorKit for Erlang-style messaging and thread management and the LLVM/Clang Static Analyzer for automatic bug detection. What else do you use?

Flickr place info now includes shape data for many places. See the Flickr code blog for more.

We’ve correlated most of Dopplr’s places with Yahoo WOE IDs using Flickr’s reverse geocoder, so we can use this data too. As an experiment, I wrote some clientside code to overlay this shape data onto the maps we use on Dopplr. Help yourself to the code if you want it: gist.github.com/25502

The March 2008 US conference season is nearly upon us. I’m just on my way back from representing Dopplr at Social Graph Foo Camp (find out more by listening to the Citizen Garden Podcast I participated in after the camp), but I’ll be back here again in three weeks.

I’m spending a few days in New York, where I’ll be hosted by the lovely Chris Shiflett, and then it’s on down to San Diego for ETech. That’ll be swiftly followed by SXSW Interactive where I’ll be on a panel entitled “Creative Collaboration: Building Web Apps Together”, about working in multidisciplinary teams. Finally, a week in San Francisco decompressing and having a few meetings.

I’m particularly excited by the trip to ETech. The last two years have brought smart people together to talk mostly Web 2.0 topics, but this year looks significantly more awesome. Full of genuinely emerging technology, the lineup looks like one Matt Jones and Tony Stark would appreciate.

Some highlights for me include a talk from Google’s economics groups on Prediction Markets, Computing for Socio-economic Development, and the excitingly-titled Antigenic Cartography: Visualizing Viral Evolution for Influenza Vaccine Design. Hope I see you there.

I’m writing my proposal today – I’m planning on pulling the very loose ramble I presented at Barcamp London on messaging architectures into a proper talk. For 2008 I’m very excited about Erlang, XMPP, message brokers such as ActiveMQ and clientside messaging with Comet. The future’s asynchronous and highly concurrent.

I’m looking forward to the face-to-face conversations of the upcoming conference season. Working on Dopplr didn’t leave much time for writing in 2007, and that’s not going to change in the near future. Right now my online tech output is most confined to tiny fragments of ideas on Twitter and random pictures on Flickr (Nokia N810 unboxing; Jawbone unboxing).

If you’ve taken the first steps in tinkering with an Arduino or similar kit, why not take it up a gear and sign up for the Hardcore Hardware Hacking Weekend in London on July 21st and 22nd? Massimo Banzi, co-creator of Arduino, will be teaching advanced hardware skills and I’ll be there to explain how to plug it all into software and the internet. I’m especially looking forward to hearing from guest speaker Moritz Waldemeyer. Places are limited and going fast.

The theme this year was ‘The Ubiquitous Web’. HTTP isn’t just for computers any more, and I’m particularly interested in how developers like me can learn to make their own network-connected objects in the real world. To spread the word, I gave a lightning talk on my experiences with the Arduino hardware hacking boards and other toys from tinker.it.

I put the slides on SlideShare.

I made a recording of the audio from the talk on my laptop’s microphone, and I’ve synchronised it with video of the slides in this Flash movie:

If you prefer, there’s also the audio-only MP3.

For the last couple of months I’ve been working on a new project in my spare time. Dopplr is a social network for frequent travellers, designed to increase the amount of serendipity in the world. It lets you share your travel plans with your trusted fellow travellers, and uses them to find the coincidences, near-misses and surprises. Maps, mobile, timelines, feeds, calendars: you can have the information pretty much any way you want it.

Dopplr’s still invite only, but there’s a good chance you know someone with an account by now. We’ll be issuing new invite tokens from time to time, so keep an eye out. There are some screenshots on Flickr, and alpha travellers Stowe Boyd and Roo Reynolds have written some illuminating reviews. I’ll be at XTech in Paris in May (don’t forget, online registration closes soon) so track me down and I’ll give you a demo.

I’m having a great time making something of my own and collaborating with people whose skills and opinions I trust and respect. I showed the alpha release around ETech and SXSW and got some great reactions. We started inviting people in to test the app, a few at a time, and their feedback has been very encouraging.

Because I’m having so much fun and I want Dopplr to be as good as it can possibly be, I’ve taken the decision to suspend my freelancing and work on it full time. It seems they’ll let anyone be a CTO these days.

If you want to follow our day-to-day progress, I’m collecting dopplr-related links and coverage on del.icio.us.

While I’m there, I’ll be hanging out at the usual places – I’m staying in the Mission so it’ll be Ritual Roasters by default. I’ll also be at the following events:

• SXSW (including Music for the first time this year)
• IA Summit (on a Web Of Data panel with Tom Coates and friends)
• ETech

I hope I see you there.