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问题:

Just a simple task, but I\'m in trouble. Trying to make a different way but it fails.

How to init NSTimer with declared previously variable? Neither var nor let helps.

回答1:

The initial value of a property (in your case: timer) cannot depend on another property of the class (in your case: interval).

Therefore you have to move the assigment timer = NSTimer(interval, ...) into a method of the class, e.g. into viewDidLoad. As a consequence, timer has to be defined as an optional or implicitly unwrapped optional.

Note also that Selector(...) takes a literal string as argument, not the method itself.

So this should work:

class ViewController: UIViewController {

    var interval : NSTimeInterval = 1.0
    var timer : NSTimer!

    func timerRedraw() {

    }

    override func viewDidLoad() {
        super.viewDidLoad()
        timer = NSTimer(timeInterval: interval, target: self, selector: Selector(\"timerRedraw\"), userInfo: nil, repeats: true)

        // ...
    }

    // Other methods ...
}

回答2:

Try:

var interval:NSTimeInterval = 1.0
var timer = NSTimer.scheduledTimerWithTimeInterval(interval, target: self, selector: \"timerRedraw:\", userInfo: nil, repeats: true)

pro-tip and hopefully an appreciated FYI: Swift functions should also start with lower case letters (i.e. \"timerRedraw\").