With the release of iOS 8 getting closer by the day, Apple has started a new blog to answer questions about Swift, the new programming language for iOS and OS X. Swift aims to make writing code more interactive and fun, while keeping apps running fast. The opening topic for the blog addresses Swift's possible compatibility issues.
Swift can work alongside Objective-C code, allowing developers to easily integrate it into their existing apps or build their own from scratch. As Swift evolves, Apple plans to provide Xcode tools to help move your old source code forward along with changes in the language.
The goal with Swift is to keep your apps working now and into the future. From the blog:
You can check out the rest of the Swift blog here, including details about Binary Compatibility and Frameworks. For more information on Swift, head over to the language's announcement page.
Simply put, if you write a Swift app today and submit it to the App Store this Fall when iOS 8 and OS X Yosemite are released, you can trust that your app will work well into the future. In fact, you can target back to OS X Mavericks oriOS 7 with that same app. This is possible because Xcode embeds a small Swift runtime library within your app's bundle. Because the library is embedded, your app uses a consistent version of Swift that runs on past, present, and future OS releases.