iOS app that has both Objective-c and Swift - pros & cons

Question

I work with an App that's 100% Objective-C and I'd like to start transitioning over to include Swift. Due to the size of the codebase, it's unrealistic that I'll have a 100% Swift app anytime soon.

As soon as a swift file is added, I noticed that the app size increases because now, the app needs to the include Swift run-time.

How else does things change? As soon as you include a Swift file, what is the process that the compiler and linker undergoes to ship a binary that is now multiple language & related frameworks?

Are there any other caveats in transitioning into a mixed language world in a somewhat large codebase?

Answer 1

In my experience, it works surprisingly well. It is advisable however, to wait to Xcode 7 / Swift 2.0 / Objective-C with generics support as that will eliminate a round of updates, allow you to interop from Objective-C with more elegant Swift code, and eliminate the Swift RT linking concern now that they have stabilized the runtime.

Aside from that, both compilers need to run, Swift first, Objective-C second, the swiftc compiler can be pretty fast or really really slow, depending on what innocent and otherwise legal Swift code that you write (this is also true of a Swift-only app of course).

Getting started, you need to read the interop guide, learn how the bridging header works, and are then mostly on your way. I would say that having a mixed app is actually a blessing as you are not pressed to learn and do everything at once. Opinions will vary of course, but this is mine.