Swift implementation of weak timer which automatically deallocates when target is released.

WeakTimer.swift

final class WeakTimer {
    
    fileprivate weak var timer: Timer?
    fileprivate weak var target: AnyObject?
    fileprivate let action: (Timer) -> Void
    
    fileprivate init(timeInterval: TimeInterval,
                     target: AnyObject,
                     repeats: Bool,
                     action: @escaping (Timer) -> Void) {
        self.target = target
        self.action = action
        self.timer = Timer.scheduledTimer(timeInterval: timeInterval,
                                          target: self,
                                          selector: #selector(fire),
                                          userInfo: nil,
                                          repeats: repeats)
    }
    
    class func scheduledTimer(timeInterval: TimeInterval,
                              target: AnyObject,
                              repeats: Bool,
                              action: @escaping (Timer) -> Void) -> Timer {
        return WeakTimer(timeInterval: timeInterval,
                         target: target,
                         repeats: repeats,
                         action: action).timer!
    }
    
    @objc fileprivate func fire(timer: Timer) {
        if target != nil {
            action(timer)
        } else {
            timer.invalidate()
        }
    }
}

// Usage:
let timer = WeakTimer.scheduledTimer(timeInterval: 2,
                                     target: self,
                                     repeats: true) { [weak self] timer in
                                         // Place your action code here.
}

Thanks for your effort.
Until now, I realise that Timer is a strong reference!

Starting from iOS 10+ you just could use:

let timer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] timer in
    // Place your action code here.
}