July 31

I'm Speaking at the "Voices that Matter" iPhone Development Conference

In October, I'll be in Boston at the "Voices that Matter" iPhone development conference put on by Pearson Education.

I'll be giving two talks:

One on Saturday about data synchronization — all I've learned from doing the Mac and iPhone versions of ShoveBox and all the funny edge cases that come up when dealing with syncing.

The other one is about getting more done in Xcode.

If you register before September 12, you can save $200 on admission. Hope to see you there!

May 13

Bonjour API Tweak in Mac OS X 10.5.7

Recently, Apple released an update to Mac OS X that broke syncing in my app ShoveBox. The app syncs over the user's local WiFi network and uses Bonjour in order to find the iPhone/iPod version of ShoveBox.

A few fellow developers were curious what was changed in 10.5.7, so I thought I'd post it here.

After some troubleshooting, I found that Apple had made a slight tweak to the way the Cocoa APIs for Bonjour work. As of 10.5.6 and below, if you called -startMonitoring on an NSNetService, it would immediately call the delegate method – netService:didUpdateTXTRecordData: to let you know that the TXT record changed or became available, even if it had not changed from when -startMonitoring was called.

I'm not sure what I was under the influence of when writing this part of ShoveBox, but I had (perhaps defensively) coded it to only count the NSNetService as a viable sync source once –netService:didUpdateTXTRecordData: was called — as it did seem to be called in every case.

As of 10.5.7, NSNetService (correctly) only calls that method once the TXT record has actually changed.

The fix involved checking for/validating the TXT record for the NSNetService as soon as its address is resolved (in – netServiceDidResolveAddress:). Now, only if it is not present and valid, it I call -startMonitoring. It should be sufficient, however, to only validate once if the broadcasting application does not change its TXT records.