Xcode 8.0 Swift 3.0 slow indexing and building

Question

I\'ve installed Xcode 8.0 and converted Swift 2.2 to 3.0 (that process also took a lot of time, I just left my Mac running all night). I have not a big project (about 20 fil

Answer 1

I had a function that took over a minute to compile, and after some investigation, I found that the culprit was checking if enough time had elapsed from a stored date:

let myStoredDate: Double = // Double representing a time in the past

// if at least one week (60 * 60 * 24 * 7 seconds) has passed since myStoredDate
if Date().timeIntervalSince1970 - myStoredDate > (60 * 60 * 24 * 7){
    // do stuff
}

This code would take over 10 seconds to compile — coupled with this code being repeated with different numbers multiple times, it was causing compilation to take way too long. I was able to fix this by pre-computing the interval

let myStoredDate = // Double representing a time in the past

//it is important to explicitly specify that the variable is a Double
let interval: Double = 60 * 60 * 24 * 7

if Date().timeIntervalSince1970 - myStoredDate > interval{
    // do stuff
}

After doing this with the ~10 times I was checking, the compilation time was cut from over a minute to just a few milliseconds.

It's extremely likely that this problem also occurs with the combination of type-inferance and math elsewhere, so ensure that nothing like this happens anywhere else in your code.