The reason for all of the now variables is that we want to get the mach_absolute_time() value as early as physically possible. In this case, the precision of the result is more important than wasting cycles asking for the value in cases where we don't end up using it.

The best way to use this timer would be to provide refTime parameter values wherever available, and for that value to be from mach_absolute_time()

This timer allows you to call result = myTimer.result(refTime: mach_absolute_time()) even when the Timer is still running. This is good for situations where you want to take "Checkpoint" times from an overall process using a single Timer.

The stop function will return the result by default.

Simple usage example:

do {
  var myTimer = try MachTimer()
  myTimer.start() // or myTimer.start(mach_absolute_time()) if you care about drift from the call stack
  // Do something here
  let pointInTime = myTimer.result() // or let pointInTime = myTimer.result(mach_absolute_time()) if you care about drift from the call stack
  // Do something else
  let totalTime = myTimer.stop() // or let totalTime = myTimer.stop(mach_absolute_time()) if you care about drift from the call stack

To use pointInTime and totalTime you can do the following:

  print("Point In Time was \(pointInTime.nanos)ns [\(pointInTime.millis)ms]")
  print("Total Time was \(totalTime.nanos)ns [\(totalTime.millis)ms]")

Don't forget to close the do block and handle the possible Error:

}
catch MachTimerError.TimebaseInfoError {
    print("Couldn't get Timebase Info!")
    exit(1)
}

You can wrap the do and catch block as close to the initialisation of your MachTimer object as you wish. Just remember that it is possible (albeit extremely unlikely) to encounter an error when the MachTimer attempts to read the mach_timebase_info(&info) which is why we have the throw and catch in the first place.

If you need to persist the instance of your MachTimer without encapsulating all of its referencing code inside of a do/catch block, you can do this:

var myTimer: MachTimer? = nil
do {
    myTimer = try MachTimer()
}
catch MachTimerError.TimebaseInfoError {
  print("Couldn't get Timebase Info!")
}

You can then do nil checks before using the Timer in the many ways Swift language supports, e.g:

if myTimer {
    // Use the Timer
}

or

if !myTimer {
    return // Early return pattern
}
myTimer!.start() // Example of asserting that myTimer cannot be nil, and call its start method

or:

myTimer?.start() // Will only invoke the start method if myTimer is not nil

or (for some versions of Swift that don't like the above)

if let actualTimer = myTimer {
    actualTimer.start()
    // Use the timer referencing actualTimer from here on
}

or (finally) you can do something similar to above, but reusing the same variable name:

if let myTimer = myTimer {
    myTimer.start()
    // Use the timer referencing myTimer
}

can you please tell me how to call in the view (like in the content view, or you need to make a class???
)