Swift - JSON函数无法正确更新

Question

I have a JSON function that gets currency exchange data, but the function is only re-sending the JSON request every 28 times. Here is my code:

func fetchPrice() {
let url = URL(string: "http://finance.yahoo.com/webservice/v1/symbols/EURUSD=x/quote?format=json")
let data = try? Data(contentsOf: url!)

do {
    let object = try! JSONSerialization.jsonObject(with: data!) as? NSDictionary

    if let dictionary = object as? [String: AnyObject] {
        let title = object?["list"] as! [String:Any]
        let title2 = title["resources"] as! [AnyObject]?
        let title3 = title2?[0] as! [String:Any]?
        let title4 = title3?["resource"] as! [String:Any]?
        let fields = title4?["fields"] as! [String:Any]?

        let price = fields?["price"] as! String

        print(fields?["price"] as! String)
        print(fields?["ts"] as! String)
        //print(NSDate().timeIntervalSince1970)
        //print(dictionary)

    }
}
}

while true {
    fetchPrice()
    sleep(UInt32(1))
}

The URL does change the price every second, but it is not working when I try to refresh every second of few seconds. It works when I re-compile my playground just not in the function.

Answer 1

Use a timer. beginFetch code will perform your fetch every second until you call stopFetch:

    var fetchTimer: Timer!

    func beginFetch() {
        var fetchCount = 0
        fetchTimer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
            fetchCount += 1
            print("\n The timer has run \(fetchCount) times")
            self.fetchPrice()
        }
    }

    func stopFetch() {
        fetchTimer.invalidate()
    }