如何在swift 3中處理錯誤？

Question

我使用下面的代碼：

let jsonData1 = (try? Data(contentsOf: URL(string: "\(label2)")!)) as Data! 
    var error : NSError? 
    let ReadableJSON1 = JSON (data:jsonData1!, options: JSONSerialization.ReadingOptions.mutableContainers, error: nil) 


    if (error != nil){ 

     let myAlert = UIAlertController(title: "Alert", message: error?.localizedDescription, preferredStyle: .alert) //you can change message to whatever you want. 
     let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil) 
     myAlert.addAction(okAction) 
     self.present(myAlert, animated: true, completion: nil) 

     return 
    } 

如果應用程序打開JSON文件形成鏈接時發現錯誤，應該顯示一個警告給用戶。目前它正在崩潰，看起來這些操作沒有執行，這就是爲什麼我沒有看到警報。你能幫我解決這個問題嗎？

Answer 1

試試這個代碼：

var json : [String: AnyObject]? // Property 
do { 
    let jsonData1 = (try? Data(contentsOf: URL(string: "\(label2)")!)) as Data! 
    json = try JSONSerialization.jsonObject(with: jsonData1, options: JSONSerialization.ReadingOptions.mutableContainers) as! [String: AnyObject] 
} 
catch let error as NSError { 
    let myAlert = UIAlertController(title: "Alert", message: error?.localizedDescription, preferredStyle: .alert) //you can change message to whatever you want. 
    let okAction = UIAlertAction(title: "Ok", style: .default, handler: nil) 
    myAlert.addAction(okAction) 
    self.present(myAlert, animated: true, completion: nil) 

    return 
} 

希望這將有助於！快樂編碼！