Timer

Timer.swift

class ThingManager {
    
    var things: [String: Thing] = [:]
    
    func addThing(_ thing: Thing) {
        self.things[thing.address] = thing
    }
    
    func removeThingWith(address: String) {
        self.things.removeValue(forKey: address)
    }
    
    fileprivate var thingWatchingQueue = DispatchQueue.main//DispatchQueue.global(qos: .utility)
    fileprivate var thingWatchingTimers: [String: Timer] = [:]
    
    func sawSomeThing(withAddress address: String) {
        self.thingWatchingQueue.async {
            // re-up the timer so we don't forget about that thing
            if let timer = self.thingWatchingTimers[address] {
                timer.invalidate()
            }
            
            self.thingWatchingTimers[address] = Timer.scheduledTimer(withTimeInterval: 5.0, repeats: false, block: { (timer) in
                self.removeThingWith(address: address)
            })
        }
    }
}