Swift NSTimer unrecognized selector sent to instance timerFireMethod - ios

Question

I'm writing some timer code in Swift for iOS 9.2
I have the latest iOS 9.2 docs downloaded through xcode
They show
(void)timerFireMethod:(NSTimer *)timer
But this will not work.
If I use signatures like these
func timerFire(timer : NSTimer?)
func timerFire(timer : NSTimer)
Then I get the error
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[DSP1.PlayManager timerFire]: unrecognized selector sent to instance
The only thing I can get to work is a call signature like this
func play(sound : String)
{
bsound = theLM?.getPlayer(sound)
bsound?.delegate = self
bsound?.play()
stimer = NSTimer(timeInterval: 1.0, target: self, selector: Selector("timerFire"), userInfo: self, repeats: true)
NSRunLoop.currentRunLoop().addTimer(stimer!, forMode: NSDefaultRunLoopMode)
}
// Docs say signature should be (void)timerFireMethod:(NSTimer *)timer. Docs are wrong
func timerFire()
{
print("Player at: \(bsound?.currentTime) out of \(bsound?.duration) seconds");
}
But this does not match what the latest iOS 9.2 docs downloaded through XCode say should work.
Am I doing this right?
Why do the freshly loaded iOS 9.2 docs seem to have the wrong signature?
What are other people reading for accurate documentation for Swift iOS programming?
(Edited to be more clear that the callback signatures listed in the docs fail to work at runtime)
Answer:
In the call to NSTimer, if your function name passed in as Selector has a trailing colon, it means you want the timer passed as an argument to your method. No colon means you don't want the timer passed as an argument.
NSTimer(timeInterval: 1.0, target: self, selector: Selector("timerFire"), userInfo: self, repeats: true)
func timerFire()
OR
NSTimer(timeInterval: 1.0, target: self, selector: Selector("timerFire:"), userInfo: self, repeats: true)
func timerFire(timer : NSTimer)
The documentation for NSTimer mentions this for the selector argument, but is far from clear. "The selector should have the following signature: timerFireMethod: (including a colon to indicate that the method takes an argument). "

Answer 1

You've made a simple, yet common mistake.
Your method signature should be:
func timerFire(timer: NSTimer) {}
And your timer setup should be:
NSTimer(timeInterval: 1.0, target: self, selector: "timerFire:", userInfo: nil, repeats: true)
The mistake is that you're missing the colon in the selector name. timerFire is different from timerFire:. Skip the colon and it'll look for for a method like this:
func timerFire() {}
Without the NSTimer parameter. It's best though to include the parameter, and thus the colon, so that you can confirm the timer you get is the one you expect.
The same is true for notifications. If you're using Notification Center, include the colon, and the Notification object in the method.

Answer 2

Your code seems to be ok. The selector for your timer does not have a predefined signature, you can all it whatever you like as long a you have a method in your class with that name.
func play(sound : String) {
// ....
stimer = NSTimer(timeInterval: 1.0, target: self, selector: "methodToRunOnTimerTick", userInfo: self, repeats: true)
NSRunLoop.currentRunLoop().addTimer(stimer!, forMode: NSDefaultRunLoopMode)
}
func methodToRunOnTimerTick() {
print("Player at: \(bsound?.currentTime) out of \(bsound?.duration) seconds");
}
One more thing to remember is that the method you decide to use can also receive the timer as a parameter when it is being called. This case would look like this:
func play(sound : String) {
// ....
stimer = NSTimer(timeInterval: 1.0, target: self, selector: "methodToRunOnTimerTick:", userInfo: self, repeats: true)
NSRunLoop.currentRunLoop().addTimer(stimer!, forMode: NSDefaultRunLoopMode)
}
func methodToRunOnTimerTick(timer: NSTimer) {
print("Player at: \(bsound?.currentTime) out of \(bsound?.duration) seconds");
}
So you implement the timer the right way, the method does not need a special signature. Let me know if you need more help. Good luck with your project!