Change userInfo in timer selector function in Swift

I want to update the userInfo of the timer in the selector function every time the timer fires.

userInfo:

var timerDic  = ["count": 0]

Timer:

Init:     let timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector:     Selector("cont_read_USB:"), userInfo: timerDic, repeats: true)

selector function:

public func cont_read_USB(timer: NSTimer)
{
  if var count = timer.userInfo?["count"] as? Int
  {
     count = count + 1

     timer.userInfo["count"] = count
  }
}

I get an error on the last line:

'AnyObject?' does not have a member named 'subscript'

What is wrong here? In Objective_C this task worked with a NSMutableDictionary as userInfo

NSTimer.userInfo is of type AnyObject so you need to cast it to your target object:

public func cont_read_USB(timer: NSTimer)
{
    if var td = timer.userInfo as? Dictionary<String,Int> {
        if var count = td["count"] {
            count += 1
            td["count"] = count
        }
    }
}