NSTimer extension which breaks the retain cycle in Swift.

nstimer_break_retain.swift

private class Block<T> {
    let f : T
    init (_ f: T) { self.f = f }
}

extension NSTimer {
    static func xxx_scheduledTimerWithTimeInterval(ti: NSTimeInterval, block: ()->(), repeats: Bool) -> NSTimer {
        return self.scheduledTimerWithTimeInterval(ti, target:
            self, selector: "xxx_blcokInvoke:", userInfo: Block(block), repeats: repeats)
    }
    
    static func xxx_blcokInvoke(timer: NSTimer) {
        if let block = timer.userInfo as? Block<()->()> {
            block.f()
        }
    }
}

@vin-zhou you can call invalidate in viewDidDisappear? Because run loop will maintain strong reference to timer, timer to ViewController. So call invalidate it first to release timer then ViewController.

Timers work in conjunction with run loops. To use a timer effectively, you should be aware of how run loops operate—see NSRunLoop and Threading Programming Guide. Note in particular that run loops maintain strong references to their timers, so you don’t have to maintain your own strong reference to a timer after you have added it to a run loop.