下标错误使用

Question

I read about this error and I know that it alerts when the compiler does not know what type it needs to return, but this error did not appear earlier and I do not know why it appears today.

This is my code:

func animateCounter(from: Int, to: Int) {
    timer = NSTimer.scheduledTimerWithTimeInterval(duration, target: self, selector: "increaseCounter", userInfo: ["from": from, "to": to], repeats: false)
}

func increaseCounter() {
    let from = timer.userInfo!["from"] as! Int
    let to = timer.userInfo!["to"] as! Int
}

I set that my from and to variables are Integers, so why I get this error?

Answer 1

Cast userInfo to Optional([String:AnyObject]) first and then cast userInfo["from"], userInfo["to"] to Optional(Int)

Your will need to unwrap the result by yourself :)

func increaseCounter() {
    let userInfo = timer.userInfo as? [String: AnyObject]
    if let dict = userInfo {
        let from = dict["from"] as? Int
        let to = dict["to"] as? Int
    }
}