 
         let intStepNo = Int(stepNo)
         let intTracks = tracks.compactMap { return $0.intValue }
+        // notify the step is triggered
         callback(intTracks, intStepNo, absoluteTime)
     }
 }


    /// Set sequence for the specified track.
    ///
    /// The sequence contains NSNumber<bool> values. The size must be equal to numSteps property.
    ///
    /// - Parameters:
    ///   - sequence: an array of bool values. true means note on.

import Foundation

public class HKLStepSequencer: NSObject {
    /// typealias for callback from the audio engine to tell that the sequencer has triggered at the step(time).
    /// It is available to show UI the specified note is ON.
    ///
    /// - Parameters:
    ///   - tracks: an array of tracks that the note is now ON
