unrecognized selector sent to instance when using NSTimer

Question

When I start my code I run into the console error

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[_SwiftValue counter]: unrecognized selector sent to instance

the code is the following

class Status: UIViewController {
    @IBOutlet var health: UIProgressView!
    @IBOutlet var happiness: UIProgressView!
    @IBOutlet var energy: UIProgressView!
    @IBOutlet var hygiene: UIProgressView!
    @IBOutlet var pain: UIProgressView!
    @IBOutlet var hunger: UIProgressView!

    var total:Double = 1

    @objc func counter() {
       total -= 0.05
    }

    let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector:#selector(counter), userInfo: nil, repeats:true)

    override func viewDidLoad() {
        super.viewDidLoad()

        hunger.setProgress(Float(total), animated: true)
        happiness.setProgress(Float(total), animated: true)
        energy.setProgress(Float(total), animated: true)
        hygiene.setProgress(Float(total), animated: true)
        pain.setProgress(Float(total), animated: true)
        health.setProgress(Float(total), animated: true)
    }
}

Also here's a picture of the full error message I am receiving Error Message

Code Different Code Different · Accepted Answer · 2018-09-02T14:22:48

When you use a default value like that, self is not yet fully initialized. Use an implicitly unwrapped optional and move the call into viewDidLoad:

var timer: Timer!

override func viewDidLoad() {
    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector:#selector(counter), userInfo: nil, repeats:true)
}

This assumes that you do not need the timer before the view controller finishes loading from nib, which should be most of the time.

unrecognized selector sent to instance when using NSTimer

1 Answers