Radical differences between iOS versions?

Question

I'm really new to iOS development, and I'm looking for docs on it. However, I don't like to stockpile a bunch of tutorials, books and courses that I may find knowing that they may differ in several aspects when changing versions.

For instance, in .NET, in which I'm much more experienced we had some major changes between .NET 1.1 to .NET 2, and some major aditions to the 3.0, 3.5 and 4, but the radical change was from 1.1 to 2.

My question is for you iPhone/iPad/iOS in general developers, have you seen any major changes in the history of iOS?, and by major I mean leaving a lot of applications with compatibility issues.

Answer 1

Seems to me the biggest change is that with the latest tools, you should use automated reference counting. Any book written prior to iOS 5 is going to have a fair amount of space covered to manual memory management.

But, this is not an API change.

Answer 2

Apple has done a good job of maintaining compatibility throughout all of the iOS updates. For the most part, even apps written for iOS2 will still work with iOS5. There are some areas that have been more built out now that weren't before. Every OS brings scattered bits that are depreciated and/or changed. But as far as sweeping changes, that has not been the case.

The most notable changes, if you are using tutorials and books to learn, are the updates to Xcode (The Integrated Development Environment - IDE) its self. If you are using an older book it might be easy to get a bit lost trying to figure out the new Xcode. But as far as code goes, most is still perfectly valid.

Some areas to be more aware of updates in:

Audio & Video

Dealing with Retina Screens

Answer 3

There have been some big changes in each version but a well written app designed for iPhone OS 2.0 will probably still compile and work with the current version of iOS. While some APIs are no longer recommended, I'm not aware of any that have actually been removed.