How to stop ViewController in Swift? - ios

Question

my ViewController is still sending an array update, even if I'm in another View, what can I do? Here is my code:
import UIKit
import CoreBluetooth
class ViewController: UIViewController {
var audioVibe : AudioVibes!
var superpowered:Superpowered!
var displayLink:CADisplayLink!
var layers:[CALayer]!
var magnitudeArray : [UInt16] = [0, 0, 0, 0, 0, 0, 0]
override func viewDidLoad() {
super.viewDidLoad()
// Setup 8 layers for frequency bars.
let color:CGColorRef = UIColor(red: 0, green: 0.6, blue: 0.8, alpha: 1).CGColor
layers = [CALayer(), CALayer(), CALayer(), CALayer(), CALayer(), CALayer(), CALayer(), CALayer()]
for n in 0...7 {
layers[n].backgroundColor = color
layers[n].frame = CGRectZero
self.view.layer.addSublayer(layers[n])
}
superpowered = Superpowered()
// A display link calls us on every frame (60 fps).
displayLink = CADisplayLink(target: self, selector: #selector(ViewController.onDisplayLink))
displayLink.frameInterval = 1
displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSRunLoopCommonModes)
}
// Gets triggered when you leave the ViewController.
override func viewWillDisappear(animated: Bool) {
superpowered.togglePlayback();
superpowered.moritz();
//delete(superpowered);
}
func onDisplayLink() {
// Get the frequency values.
let magnitudes = UnsafeMutablePointer<Float>.alloc(8)
superpowered.getMagnitudes(magnitudes)
// Wrapping the UI changes in a CATransaction block like this prevents animation/smoothing.
CATransaction.begin()
CATransaction.setAnimationDuration(0)
CATransaction.setDisableActions(true)
// Set the dimension of every frequency bar.
let originY:CGFloat = self.view.frame.size.height - 20
let width:CGFloat = (self.view.frame.size.width - 47) / 5
var frame:CGRect = CGRectMake(20, 0, width, 0)
for n in 0...4 {
frame.size.height = CGFloat(magnitudes[n]) * 2000
frame.origin.y = originY - frame.size.height
layers[n].frame = frame
frame.origin.x += width + 1
}
// Set the magnitudes in the array.
for n in 0...6 {
magnitudeArray[n] = UInt16(magnitudes[n] * 32768)
}
// Update the array in the audioVibe class to trigger the sending command.
audioVibe.magnitudeArray = magnitudeArray
CATransaction.commit()
// Dealloc the magnitudes.
magnitudes.dealloc(8)
}
}
I want him to stop doing things like audioVibe.magnitudeArray = magnitudeArray while I'm not in his view, what can I do?
Thanks!

Answer 1

Looks like you display link isn't getting paused when you transition to different views.
You could pause your display link when transitioning away from this view and resume it when coming back to this view using the paused property on CADisplayLink. You would pause it in viewWillDisappear and resume in viewWillAppear.

Answer 2

In your viewDidLoad method you're creating a CADisplayLink and adding it to the run loop.
If you don't do anything, that display link will stay active when you push another view controller on top of it.
You should move the code that creates the display link and adds it to the run loop to your viewWillAppear method.
Then you need to add code in viewWillDisappear that removes the display link from the run loop, invalidates it, and nils it out.
That way, you'll start your display link code when the view appears, and stop it when the view disappears.