NSTimer.scheduledTimerWithTimeInterval in Swift Playground - swift

Question

All the examples I've seen on using the "NSTimer.scheduledTimerWithTimeInterval" within Swift show using the "target: self" parameter, but unfortunately this doesn't work in Swift Playgrounds directly.
Playground execution failed: <EXPR>:42:13: error: use of unresolved
identifier 'self'
target: self,
Here's an example referenced above that results in the error:
func printFrom1To1000() {
for counter in 0...1000 {
var a = counter
}
}
var timer = NSTimer.scheduledTimerWithTimeInterval(0,
target: self,
selector: Selector("printFrom1To1000"),
userInfo: nil,
repeats: false
)
timer.fire()

Answer 1

You really should not be using NSTimer these days. It's consumes a lot of resources, causes unnecessary battery drain, and the API lends itself to ugly code.
Use dispatch_after() instead:
dispatch_after(0, dispatch_get_main_queue()) { () -> Void in
for counter in 0...1000 {
var b = counter
}
}
Of course, since the timer will fire after playground does it's stuff you will need an equivalent of timer.fire() to force the code to execute immediately instead of after a 0 second delay. Here's how that works:
let printFrom1To1000 = { () -> Void in
for counter in 0...1000 {
var b = counter
}
}
dispatch_after(0, dispatch_get_main_queue(), printFrom1To1000)
printFrom1To1000()

Answer 2

To get this to run directly within a Swift Playground, you need to embed the printFrom1To1000 function within a class and then set an instance of that class to the "target:" parameter instead of using "self".
Here's a full working example:
class myClass: NSTimer{
func printFrom1To1000() {
for counter in 0...1000 {
var b = counter
}
}
}
let myClassInstance = myClass()
var timer = NSTimer.scheduledTimerWithTimeInterval(0,
target: myClassInstance,
selector: Selector("printFrom1To1000"),
userInfo: nil,
repeats: false
)
timer.fire()

Answer 3

If you already have an object you are referencing (i.e., updating a label), you can extend that type and use that function as the Selector. I find this easier than creating a whole new class and instantiating a new object from it.
extension SKLabelNode {
func updateMe() {
count++
label.text = "\(count)"
}
}
var timer = NSTimer.scheduledTimerWithTimeInterval(0.25,
target: label,
selector: Selector("updateMe"),
userInfo: nil,
repeats: true)
timer.fire()