Is developing for ios 7 different than ios 8?

With iOS8 and OS X 10.10 Apple introduced a new programming language called Swift, they've also added some new APIs to their existing frameworks that work with their new language and their existing language, Objective-C.

Swift seems to have an easier learning curve versus Objective-C, depending on the apps you want to make you'll probably be spending most of your time working within Apple's frameworks which while they are accessed differently between Objective-C and Swift, are complex all on their own.

You don't have to wait until iOS 8 or OS X 10.10 is announced to start learning Swift you can downloaded the latest Xcode 6 beta 5 from Apple and start learning. Apple's documentation is also available in the developer center and via iBooks.

There are a ton of tutorials at udemy, youtube and all around the web as well.

You can also learn Objective-C, you'll need to have an understanding of what Objective-C is and some of the basics as you're likely to interact with Objective-C for quite some time.

 

If you don't plan on using any of the new iOS 8 APIs, developing for iOS 8 is nearly identical to developing for iOS 7. You don't have to use most of the new iOS 8 APIs or Swift to code a working app, although a few of the new APIs might fix minor problems. Most (but not all) apps developed with the iOS 7 SDK and Xcode 5.1 seem to run just fine on iOS 8 beta test devices. (I even found a few old apps developed for obsolete iOS 3 and iOS 4 that still run just fine on iOS 8 test devices. So 8 is showing good compatibility with earlier coding.)

Of course, a lot of people are betting that Swift will be the iOS development language to learn... next year. (It's still way too broken/unfinished this summer. The books will follow even later.)