As Apple moves Mac OS X toward iOS-like behaviour, the filesystem on Macs is slowly withering away. New features such as versions are accessible only from within an application. iCloud syncing doesn't work on arbitrary files, but on documents, again from within an application.

All this is to get away from having users use the filesystem. That's not a bad goal, since the filesystem is one of the bits of legacy that nerds understand but regular people don't. Real appliances won't have user-visible filesystems.

One aspect of Apple's iOS approach is that documents belong to a single app. There is no arbitrary data lying around, and no files that are equally shared by several applications in concert. It appears they're trying to keep to a simple mental model of how documents work, so non-nerds will be able to use the device properly.

Unix, on the other hand, loves files made up of arbitrary (generally textual) data that many apps access. The data itself is primary and standalone. Programs were often written to conform to data conventions, so the files could be operated on by any program. The Mac/iOS way is to have the app be primary, and it solely owns any data it needs to do its job.

The Unix Way and the Mac/iOS Way are incompatible. As one becomes more prevalent, the other will be harder.

So What?

Many unix programmers migrated to the Mac because it was the best unix-like system. You got the slick Mac GUI, but could compile source or get binaries for very nearly any unix program you could enjoy on the free unixes. But as Apple moves to iOS-ify the Mac, ported unix utilities will operate farther and farther from the Mac Way. MacVim, for example, will never support Lion's AutoSave and Versions. This is not because it's too hard — it's because those features don't make sense with the way Vim works.

So what does this mean for programmers on the Mac Platform? As the gap between Mac and Unix conventions widen, will dissonance push unix developers off? Where will they go? Or will there just be a growing difference between a developer's Mac and a regular user's?

I'm not complaining about the iOS-ification of the Mac. Computers have to become appliances if they're to be used heavily by the general public. It's that I am so used to the development platform also being the general-purpose computing platform. It will be interesting to observe the end of that relationship.