NSTimer, setNeedsDisplay, unrecognized selector issues - ios

Question

The logic for this app is functioning, but the timer is not functioning properly. I have three files: ViewController.Swift, clock.swift, and clockstylekit.swift.
updateTime(), located in the clock.swift file pulls the time, breaks it into its components, and returns hours, minutes and seconds and summons drawRect to redraw the visual representation of the time.
import UIKit
import Foundation
class timeUpdate: UIView {
func updateTime() -> (Int, Int, Int) {
var date:NSDate = NSDate()
var calendar:NSCalendar = NSCalendar.currentCalendar()
var components:NSDateComponents = calendar.components(NSCalendarUnit.CalendarUnitHour | NSCalendarUnit.CalendarUnitMinute | NSCalendarUnit.CalendarUnitSecond, fromDate: date)
var hour = components.hour
var minute = components.minute
var second = components.second
setNeedsDisplay()
return (hour, minute, second)
}
}
The drawRect() method also located in the clock.swift file draws out the time components to a UIView:
class clock: UIView {
override func drawRect(rect: CGRect) {
let (hour, minute, second) = timeUpdate().updateTime()
switch hour {
case 0:
ClockStyleKit.drawCanvas0()
case 01, 13:
ClockStyleKit.drawCanvas0()
ClockStyleKit.drawCanvas01()
.....etc etc
}
}
This is the timer I am using:
var timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("updateTime"), userInfo: nil, repeats: true)
When I put this into the ViewController viewDidLoad function, I get an unrecognized selector error. When I place this into a function in my clock.swift file, I can compile without any errors, the time is updated properly, but it only runs once and does not update. Where should this timer go?

Answer 1

The signature for your timer function is wrong. According to the documentation the selector must have the following signature:
- (void)timerFireMethod:(NSTimer *)timer
So you need to create a timer method something like:
func updateTime(time:NSTimer) {
// your code here
}
Then call it using Selector(updateTime:)
I would suggest that you simply have the timer request the clock display to refresh and in the display code calculate the time just before you display it.

Answer 2

If that var timer = NSTimer... code is in your ViewController function, then self is going to be the ViewController. In your timer, you set the target to be equal to self so it's going to look for a method called updateTime in your ViewController, and it's not there because it's in the TimeUpdate class. Also, your selector's signature is wrong. You're calling updateTime(), but it wants to be calling a selector with a parameter of NSTimer that returns a void, so you need to call a routine with this signature:
func firedTimerMethod(timer: NSTimer)
Reread the description of NSTimer in the docs in Xcode.

Answer 3

What I had to do was place my timer in my viewcontroller like so:
class ViewController: UIViewController {
var timer = NSTimer()
override func viewDidLoad() {
super.viewDidLoad()
self.timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("firedTimerMethod:"), userInfo: nil, repeats: true)
}
#objc func firedTimerMethod(timer: NSTimer) {
println("firedTimerMethod fired")
let clockView = self.view as! clock
clockView.setNeedsDisplay()
}
}
The timer's selector function needed the NSTimer parameter, the #objc, and I had to cast the variable as the clock class. Once I did these things, drawRect now properly updates each second the timer runs. I appreciate the help from everyone, all of the various clues got me on the right track eventually.