What does "% is unavailable: Use truncatingRemainder instead" mean?

Question

I get the following error when using code for an extension, I'm not sure if they're asking to just use a different operator or modify the values in the expression based on an internet search.

Error: % is unavailable: Use truncatingRemainder instead

Extension code:

extension CMTime {
    var durationText:String {
        let totalSeconds = CMTimeGetSeconds(self)
        let hours:Int = Int(totalSeconds / 3600)
        let minutes:Int = Int(totalSeconds % 3600 / 60)
        let seconds:Int = Int(totalSeconds % 60)

        if hours > 0 {
            return String(format: "%i:%02i:%02i", hours, minutes, seconds)
        } else {
            return String(format: "%02i:%02i", minutes, seconds)
        }
    }
}

The error(s) occur when setting the minutes and seconds variables.

Answer 1

CMTimeGetSeconds() returns a floating point number (Float64 aka Double). In Swift 2 you could compute the remainder of a floating point division as

let rem = 2.5 % 1.1
print(rem) // 0.3

In Swift 3 this is done with

let rem = 2.5.truncatingRemainder(dividingBy: 1.1)
print(rem) // 0.3

Applied to your code:

let totalSeconds = CMTimeGetSeconds(self)
let hours = Int(totalSeconds / 3600)
let minutes = Int((totalSeconds.truncatingRemainder(dividingBy: 3600)) / 60)
let seconds = Int(totalSeconds.truncatingRemainder(dividingBy: 60))

However, in this particular case it is easier to convert the duration to an integer in the first place:

let totalSeconds = Int(CMTimeGetSeconds(self)) // Truncate to integer
// Or:
let totalSeconds = lrint(CMTimeGetSeconds(self)) // Round to nearest integer

Then the next lines simplify to

let hours = totalSeconds / 3600
let minutes = (totalSeconds % 3600) / 60
let seconds = totalSeconds % 60