How can I transfer UISlider value on SecondViewController to Alarm on FirstViewController? - swift

Question

I have two ViewControllers, FirstViewController and SecondViewController.
And there is UISlider on SecondViewController. There is an alarm on FirstViewController.
Now I want to transfer UISlider value, which is volume to alarm on FirstViewController.
ps. The function what I want to make is totally same as default iPhone setting slider.
I would be so happy so if you guys give me your knowledge, please.
import UIKit
import AVFoundation
class FirstViewController: UIViewController, AVAudioPlayerDelegate,
UITableViewDelegate, UITableViewDataSource{
let TODO = ["A", "B", "C"]
let notificationCenter = NotificationCenter.default
var volume = Float()
var counter = 0
var timer = Timer()
var startTime:Double = 0.0
var audioPlayer: AVAudioPlayer!
#IBOutlet weak var tableView: UITableView!
#IBAction func firstSwitch(_ sender: UISwitch)
{
if (sender).isOn
{
timer = Timer.scheduledTimer(withTimeInterval: 1 * 1, repeats: false, block: { timer in
self.audioPlayer.play()
self.audioPlayer.numberOfLoops = -1
print(self.audioPlayer.isPlaying)
})
}else{
timer.invalidate()
print("switch1stopped")
self.audioPlayer.stop()
}
}
notificationCenter.addObserver(self, selector: #selector(catchNotification(notification:)), name: NSNotification.Name(rawValue: "test"), object: nil)
}
#objc func catchNotification(notification: Notification) -> Void {
print("Catch notification")
audioPlayer.volume = volumeChane.value
//Use of unresolved identifier 'volumeChane'
}
///////////////////////////////////////////////////////////////////////////
import UIKit
import AVFoundation
class SecondViewController: UIViewController {
var audioPlayer: AVAudioPlayer!
let notificationCenter = NotificationCenter.default
#IBOutlet weak var volumeSlider: UISlider!
#IBOutlet weak var volumeLabel: UILabel!
#IBAction func volumeChange(_ sender: UISlider)
{
volumeLabel.text = String(Int(sender.value))
volumeSlider.value = sender.value
audioPlayer.volume = volumeSlider.value
notificationCenter.post(name: NSNotification.Name(rawValue: "test"), object: nil)
audioPlayer.play()
}
override func viewDidLoad()
{
super.viewDidLoad()
if let url=Bundle.main.url(forResource:"Alarm",withExtension:".mp3" )
{
do {
audioPlayer = try AVAudioPlayer(contentsOf:url)
audioPlayer?.play(atTime:1 * 10)
}catch{
audioPlayer = nil
}
}else{
fatalError("Url is nil")
}
}
extension Notification.Name
{
static let myNotificationName = Notification.Name("test")
}

Answer 1

Using NSNotificationCenter for a simple task such as this might be an overkill. You usually use closures to catch data changes in your components or view controllers.
In the SecondViewController create a variable containing a closure:
var onVolumeChange: ((value: Float) -> Void)?
Call it in the IBAction that monitors slider's onChange event.
#IBAction func volumeChange(_ sender: UISlider)
{
self.onVolumeChange?(sender.value)
}
Pass the onVolumeChange closure from the FirstViewController when navigating to the second one. I'm not sure how you perform navigation so I'll assume you do it programmatically.
let vc = UIStoryboard(name: "main", bundle: nil).instantiateViewController(withIdentifier: "SecondViewController")
vc.onVolumeChange = { value in
audioPlayer.volume = value
}
self.navigationController?.pushViewController(vc, animated: true)