Calling function in ViewDidLoad through NSTimer - swift - ios

Question

I'm trying to animate some bezier paths in swift, and I need to get some of them to launch after a set delay. To do this, I have to write both of these sets of code in the viewDidLoad function.
Here is some sample code with the same idea:
override func viewDidLoad() {
super.viewDidLoad
func testFunc() {
println("Hello")
}
var frontOfBaseTimer = NSTimer.scheduledTimerWithTimeInterval(3, target: self, selector: Selector("testFunc"), userInfo: nil, repeats: false)
}
This would crash the app 3 seconds after the view loaded. The error message leads me to believe that the only problem in this case is the target property.
What should I change here to get this to work?

Answer 1

If you're bound and determined to use your own delay loop, consider using GCD and the dispatch_after method. That method takes a closure and invokes the closure after a specified delay, which is pretty much exactly what you want. You would pass nil for the queue parameter so your closure would be run on the main queue.
I created a global function delay that lets me invoke dispatch_async painlessly without having to figure out it's confusing parameters:
func delay(delay: Double, block:()->())
{
let nSecDispatchTime = dispatch_time(DISPATCH_TIME_NOW,
Int64(delay * Double(NSEC_PER_SEC)));
let queue = dispatch_get_main_queue()
dispatch_after(nSecDispatchTime, queue, block)
}
You call it like this:
delay(2.0)
{
//code to fire after a delay
}

Answer 2

try this:-
override func viewDidLoad() {
super.viewDidLoad()
var frontOfBaseTimer =
NSTimer.scheduledTimerWithTimeInterval(3,
target: self,
selector:"testFunc",
userInfo: nil,
repeats: false)
}
func testFunc(){
println("hello its me")
}

Answer 3

Do like this way, Your app get crash because, timer call the function which has been added in viewdidload method.
override func viewDidLoad() {
super.viewDidLoad()
var frontOfBaseTimer =
NSTimer.scheduledTimerWithTimeInterval(3,
target: self,
selector: Selector("testFunc"),
userInfo: nil,
repeats: false)
}
func testFunc() {
println("Hello")
}

Answer 4

I just tested it and confirmed that you can't use a nested function as the selector for an NSTimer. The method the timer calls needs to be defined at the global scope of the target.
If you're trying to do animation, why not use UIView animation? That family of methods includes a delay parameter.
You could also use Core Animation. You can animate a path very easily by installing the CGPath from a bezierPath into a shape layer, then changing the shape layer's path as part of a CABasicAnimation.
Using Core Animation makes for very smooth, clean animations.
I have a project called RandomBlobs on Github that shows how to animate Bezier paths using CAShapeLayers and CABasicAnimations. It's written in Objective-C, but the techniques are directly applicable in Swift.
You can see a short video of the bezier path animation on Youtube.