Trying to play a sound using AVFoundation - swift

Question

I am quite new to Xcode therefore apologies if the below requires a simple fix. Have created a simple button as a test for a different project, imported the mp3 file under the "Supporting Files" directory and the below is my code which is giving a number of errors due to tutorials I followed which were all using different versions of Xcode.
AVFoundation was also added to the project.
Errors:
Argument labels '(_:, error:)' do -- Extra argument 'error' in call
Use of unresolved identifier 'alertSound'
Code:
import UIKit
import AVFoundation
class ViewController: UIViewController {
var AudioPlayer = AVAudioPlayer()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let alertSound = NSURL(fileURLWithPath: Bundle.main.path(forResource: "two", ofType: "mp3")!)
print(alertSound)
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)
AVAudioSession.sharedInstance().setActive(true, error: nil)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func n2(_ sender: UIButton) {
var error:NSError?
AudioPlayer = AVAudioPlayer(contentsOfUrl: alertSound, error: &error)
AudioPlayer.prepareToPlay()
AudioPlayer.play()
}
}

Answer 1

For the first error:
Argument labels '(_:, error:)' do -- Extra argument 'error' in call
Objective C function which contains an error parameter and returns a boolean will be marked as a function which can potentially throw exceptions in Swift 3. You can handle the error using a do..try..catch construct.
You can check Apple Documentation on error handling here:
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html
The other error related to the AudioPlayer variable being a local variable which is being accessed outside of the scope.
var AudioPlayer = AVAudioPlayer()
// Declare alertSound at the instance level for use by other functions.
let alertSound = URL(fileURLWithPath: Bundle.main.path(forResource: "two", ofType: "mp3")!)
override func viewDidLoad() {
super.viewDidLoad()
print(alertSound)
do {
try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
try AVAudioSession.sharedInstance().setActive(true)
}
catch {
print("ERROR: \(error.localizedDescription)")
}
}
#IBAction func n2(_ sender: UIButton) {
do {
AudioPlayer = try AVAudioPlayer(contentsOf: alertSound)
AudioPlayer.prepareToPlay()
AudioPlayer.play()
}
catch {
print("ERROR: \(error.localizedDescription)")
}
}