Measure Function Performance in Swift

It's simple.

At the start of the function add:

let start = mach_absolute_time()

and at the end of the function add:

let endNano = mach_absolute_time() - start
let endSec = TimeInterval(endNano) / TimeInterval(NSEC_PER_SEC)
print("\(#function) - \(endSec)")

For example:

override func viewDidLoad() {
    let start = mach_absolute_time()
    super.viewDidLoad()
    …
    //    do other stuff
    …
    let endNano = mach_absolute_time() - start
    let endSec = TimeInterval(endNano) / TimeInterval(NSEC_PER_SEC)
    print("\(#function) - \(endSec)")
}

Easy.