Comment by mojuba

As long as you use the standard AU components which themselves are written in C, you should be fine. However, just one step outside of the standard functionality, e.g. you want to process or generate the audio sample stream yourself in Swift, is where it can become troublesome. I tried to profile my audio processing loops and I saw the bottlenecks in some RTL functions that deal with Swift protocols. Like I said in the other comment, I will remove protocols from that part of my code and lose much of its "swifty-ness" but then why would I even write it in Swift?