TimeElapsed.swift

class TimeElapsed: CustomStringConvertible {
    private let startTime: CFAbsoluteTime
    private var endTime: CFAbsoluteTime?

    init() {
        startTime = CFAbsoluteTimeGetCurrent()
    }

    var description: String {
        time
    }

    var time: String {
        let format = String(format: "%.5f", duration)
        let string = "[\(format)s]"
        return string
    }

    var duration: Double {
        let endTime = CFAbsoluteTimeGetCurrent()
        return endTime - startTime
    }
}


let timer = TimeElapsed()

// do some lengthy task here 

print("Time elapsed: \(timer)")