[zomgbbq]

I hear this argument a lot that it's not production ready but my personal experience does not agree. I use Swift in production for several apps with relatively large codebases that sustain many hundreds of thousands of sessions per day. I would agree that a full clean/rebuild is not as fast as Objective-C and that the incremental build system sometimes seem as though it is compiling more files than you'd like. However, for most part the incremental build system is fine and in daily use it is not a problem. I could never imagine going back to writing objective-C again when I compare the net gains we've realized coding in Swift. The readability and succinctness of the language, as well as catching bugs at compile-time rather than run-time, is a huge benefit. Value-based programming, functional(-ish) programming, and protocol extensions have made my code so much easier to maintain and test, as well.

[mahyarm]

How many lines of code does your project use? How complicated is your module structure? Is everything in one huge target or do you split your app into 100s of modules? What do you use for dependency management, what is your deployment target? Are things running in one process like an iOS app or is it some sort of OS X project?

Pretty much every large swift project I've seen has had the problems described. Lyft, Uber, Linked In, etc.

[zomgbbq]

I'm going to answer but I should preface by saying I'm not going to try to proselytize you to Swift. If it doesn't work for you and you're happy with Objective-C, then by all means do what makes you happy and keeps you productive. I have a couple of apps that have about 50k lines of Swift, one also with 60k lines of Objective-C and another with 40k lines of Objective-C. We use MVVM as well as a fairly involved mechanism of VM abstraction with intercommunication using RAC. Common code is in a cocoapod as well as other third-party dependencies otherwise the other target is the iOS app itself. I think LOC is a poor metric to measure complexity, but it does have a relevance to compile time. Others have also said that Swift and Xcode are not perfect, but as an engineer programming in Swift makes me quite happy.

[mahyarm]

Aha! You haven't hit the LOC barrier that starts to make swift & xcode/source kit act like bsaul described. At around 100kloc you will start to get that experience with swift. While an equivalent 100-200kloc line app written in objective c will work quite fine with xcode. You'll start noticing some degradation as you get to 60-70kloc. You also have a simple module structure, which makes things better.

You can see it happen pretty plainly with a simple codegen script creating a bunch of dummy code up to X lines of code.

[G4BB3R]

Then, it's not Swift that is not production ready, but XCode that is crap :)

[mahyarm]

Most of this crap comes from the compiler / sourcekit itself, which is a major part of the language. It has scalability problems.

[rimantas]

You worked with source of both, Uber and Lyft? And Linkdin too?

[mahyarm]

They do presentations about swift and have twitter employee accounts where they complain about swift :)

[nodamage]

I like Swift but incremental builds are very much broken on Xcode 8 and have been for a while: https://forums.developer.apple.com/thread/62737

This leads to very long compile times for even simple one line changes.