Question

所以我试图从Parse那里得到一个对象，它给我一个关于可选的错误，我无法理解。错误与getObjectInBackgroundWithId部分有关，我无法弄清楚为什么我的解包不起作用。

import UIKit
import Parse

class ViewController: UIViewController {

var question: String!
var answers: [String]!
var answer: String!


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a     nib.



}

func CallData() {
    var query : PFQuery = PFQuery(className: "QuestionsAndAnswers")
    query.getObjectInBackgroundWithId("myParseCode") {
        (ObjectHolder : PFObject?, error : NSError?)-> Void in
        // error is here^^
        if (error == nil) {
            self.question = objectHolder["Question"] as? String
            self.answers = objectHolder["Answers"] as? Array
            self.answer = objectHolder["Answer"] as? String

            if (self.answers?.count > 0) {
                self.questionLabel.text = self.question
            }

        } else {
            println("Theres been an error")
        }

    }
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.

Answer 1

您需要确保在将字符串分配给您的类属性之前将其解包，因为您已声明该字符串是非可选的（使用!）。您可以使用optional binding替换您提供的代码中的以下代码行：

self.question = objectHolder["Question"] as? String
self.answers = objectHolder["Answers"] as? Array
self.answer = objectHolder["Answer"] as? String

使用：

if let question = objectHolder["Question"] as? String {
    self.question = question //it's now unwrapped and not an optional
}

if let answers = objectHolder["Answers"] as? Array {
    self.answers = answers
}

if let answer = objectHolder["Answer"] as? String {
    self.answer = answer
}

用于解析的getObjectInBackgroundWithID但是＃34;不能使用参数类型＆＃34; Swift中的错误

1 个答案: