so_44390046.swift

//
//  ViewController.swift
//  so_44390046
//
//  Created by Olha Pavliuk on 6/12/17.
//  Copyright © 2017 olia. All rights reserved.
//

import UIKit
import AVFoundation
import Foundation

class ViewController: UIViewController {
    
    var currentAsset: AVAsset?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.trimmingFunc()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    func trimmingFunc() {
        
        let audioURL = URL.init(fileURLWithPath: Bundle.main.path(forResource: "Be That Man", ofType: "mp3")!)
        
        print("audioURL=\(audioURL)")
        currentAsset = AVAsset(url: audioURL)
        let options = NSKeyValueObservingOptions([.new, .old, .initial, .prior])
        currentAsset!.addObserver(self, forKeyPath: "duration", options: options, context: nil)
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        // do something upon notification of the observed object
        
        print("\(keyPath): \(change?[.newKey])")
        
        print(CMTimeGetSeconds(currentAsset!.duration)) //This is printing 0
    }
}