Apple’s new Swift language explained: A clever move to boost iOS, while holding Android apps back

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While Apple’s WWDC keynote yesterday was full of exciting new changes and features, one piece of news caught everyone off guard: With iOS 8 and OS X 10.10, and the the latest version of the Xcode developer tools, Apple has introduced a whole new programming language called Swift. According to Apple, Swift will make it a lot easier and more fun to develop apps for both iOS and OS X — in contrast to the current language, Objective-C, which has been likened by esteemed programmers to pulling teeth. Swift will also apparently bring a significant performance boost over Objective-C programs.
While Apple is being fairly coy about the exact reasoning behind the launch of Swift, it’s probably to reel in more developers, who will then create more apps, ensuring the continued dominance of iOS app ecosystem. But hey, we’re getting ahead of ourselves: What is the Swift programming language, anyway? And how can switching to a new programming language provide a massive 50% performance boost over a language that is already considered to be pretty fast?

What is Swift?

A small example of some Swift source code

For a start, the Swift language bears no relation to the Swift (A6) CPU architecture or the existing Swift parallel scripting language. Obviously, when Apple decides on a name for a product, it doesn’t let existing products or trademarks get in the way.

In the words of Apple, Swift is like “Objective-C without the C.” The introduction to Swift on the Apple developer website outlines Swift as safe, concise, and interactive (your code is interpreted and rendered in a live “Playground” view in the Xcode IDE).

In this context, “safe” mostly refers to the fact that the language is type safe — but thanks to type inference, type declarations are less onerous, making Swift more concise than C or Objective-C. The Switch statement is also is also safer and easier to use than the C counterpart. The two-phase initialization process for classes, slightly tweaked from the Objective-C way of doing things, also improves safety. Along with type inference, Swift also introduces very concise closures (lambdas).

A larger Swift source code sample, this time showing the Switch statement. It’s fairly human-readable, even for non-programmers.

On the compilation and runtime side of things, Swift targets the same Cocoa (OS X) and Cocoa Touch (iOS) APIs, and uses the same LLVM as Objective-C. Swift code can co-exist with Objective-C code in the same project, encouraging adoption.

A deep analysis of Swift is beyond the scope of this story, but in general it shares a lot of similarities with other modern languages, such as Rust, with a lot of popular ideas and patterns that have been assimilated from other languages. There will be a lot of cries that Apple copied/imitated/ripped off other languages — but ignore them. When it comes to programming languages, this kind of imitation and embrace-and-extent evolution is the norm, and a sign that everything is working as intended.

For programmers and the otherwise technically inclined, Apple has published a free 500-page Swift Programming Language book if you want to learn more about the language. You’ll need an Apple Developer account (free) to download the beta of Xcode 6, which fully supports Swift.

 Swift performance, compared to Python and Objective-C

Will Swift apps be faster than Objective-C apps?

On stage at WWDC, Apple’s Craig Federighi showed some interesting graphs that appeared to show a huge 40-50% performance lead for Swift over Objective-C. He did not say that apps written in Swift would be faster than Objective-C, though. And he was very picky about which benchmarks he showed. In reality, Swift is very unlikely to be significantly faster than Objective-C. They are both statically typed, compiled languages — using the same LLVM compiler, no less. To obtain such a graph, Apple probably had to choose an Objective-C feature that is known to be slow/buggy — or intentionally optimize a Swift feature, purely for the sake of producing a pretty graph.

We look forward to doing some real benchmarking in the coming weeks and months, though, as Swift apps start pop up on the App Store.

Why did Apple release Swift?

It all boils down to this question. Why, with a huge pool of developers who are already very knowledgeable in the ways (and quirks) of Objective-C, is Apple releasing a new programming language? Doesn’t the world already have enough programming languages? Why didn’t Apple choose another modern language, like Rust or Go?
There are a variety of possible answers, depending on how cynical you are. The nicest explanation is that Objective-C is a horrible language to learn — and so the introduction of Swift will massively increase the number of developers who are happy and willing to develop iOS and OS X apps. (The counterpoint to this is that we may then see a lot more junk apps in the App Store.)

The LLVM logo

A more complete explanation is that Objective-C is an old language — it just had its 30th birthday — and so it does make sense to introduce a newer language that more closely conforms to the modern methods of app development. As a corollary to this, Apple is the creator and curator of Swift, meaning it has a lot more flexibility to add and change functions as time goes by, rather than being forever shackled by the Objective-C framework. Think of it as an investment in the future.
The cynical explanation is that Apple wants to use its heft to weaken the Android app ecosystem. Thanks to their shared support for C, and tools to port Objective-C to Java, it’s currently fairly easy to port an app from iOS to Android. Porting Swift apps to Android, on the other hand, would be a lot more time consuming.
In reality, it’s probably a mix of all three reasons. Ultimately, there are a lot of good reasons for creating your own, tailor-made programming language. The difficult bit is in getting people to use and embrace the new language. Apple, with its captive army of millions of developers, certainly won’t have that problem.