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无法为“[UInt32]”类型的值下标

  •  1
  • Tom Fox  · 技术社区  · 9 年前

    我有一个随机生成的数字数组,然后我试图向Firebase查询一个与所选数字数组中索引[0]处的值相等的问题。现在的问题是我出错了 Cannot subscript a value of type '[UInt32]' .P.S.我对swift不是很有经验,所以精确的代码解决方案将非常精确!我还附上了我的火力基地结构。。。

    import UIKit
    import Firebase
    
    class QuestionViewController: UIViewController {
    
    
    let ref = Firebase(url: "https://123test123.firebaseio.com/questions")
    
    override func viewDidLoad() {
        super.viewDidLoad()
    
        // An empty array to hold the selected numbers
        var selectedNumbers: [UInt32] = []
    
        // A range of acceptable numbers
        let randomNumberRange = 1...10
    
        // How many numbers are needed?
        let randomNumbersToChoose = 10
    
        // Crash if asking for more numbers than are available in the range
        assert(randomNumberRange.count >= randomNumbersToChoose, "Must have enough numbers to choose from!")
    
        // Repeat this loop until all enough numbers have been selected
        while selectedNumbers.count < randomNumbersToChoose {
    
            // Pick a random number within the allowed range
            let selectedNumber = arc4random_uniform(UInt32(randomNumberRange.endIndex - randomNumberRange.startIndex)) + UInt32(randomNumberRange.startIndex)
    
            // If it's not already in the selected array, add it
            if (selectedNumbers.indexOf(selectedNumber) == nil) {
                selectedNumbers.append(selectedNumber)
            }
        }
    
        // Print the result
        print(selectedNumbers)
    
    
            print(selectedNumbers)
            let selectedNumberIndex: UInt32 = 2
            ref.queryOrderedByChild("value").queryEqualToValue(selectedNumbers[0])
                .observeEventType(.ChildAdded, withBlock: {
                    snapshot in
                    //Do something with the question
                    print(snapshot.key)
                    print(snapshot.value.valueForKey("question"))
                })
        }
    
    @IBAction func truepressed(sender: AnyObject) {
    }
    
    @IBAction func falsePressed(sender: AnyObject) {
    }
    
    }
    

    JSON数据:

    {
      "question1" : {
        "answer" : "Nohghpe",
        "question" : "Do you know swift",
        "value" : 1
      },
      "question10" : {
        "answer" : "A fdsbit",
        "question" : "Do you kndfggow firebase",
        "value" : 10
      },
      "question2" : {
        "answer" : "A bfhit",
        "question" : "Dodhfg you know firebase",
        "value" : 2
      },
      "question3" : {
        "answer" : "A bsdit",
        "question" : "Do you know firebsgdfase",
        "value" : 3
      },
      "question4" : {
        "answer" : "A vcxbit",
        "question" : "Do yosgfdu know firebase",
        "value" : 4
      },
      "question5" : {
        "answer" : "A bivcxt",
        "question" : "Do you kfghnow firebase",
        "value" : 5
      },
      "question6" : {
        "answer" : "A bxcvit",
        "question" : "Do you know fnhirebase",
        "value" : 6
      },
      "question7" : {
        "answer" : "A bivxct",
        "question" : "Do you sgdfknow firebase",
        "value" : 7
      },
      "question8" : {
        "answer" : "A bivcxt",
        "question" : "Do you knsfdow firebase",
        "value" : 8
      },
      "question9" : {
        "answer" : "A bdsfit",
        "question" : "Do you kdfgnow ffsdirebase",
        "value" : 9
      }
    }
    
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  •  8
  •   dfrib    9 年前

    这是Swift编译器掩盖另一个错误背后真实错误的典型情况。这个 .queryEqualToValue(..) method 应为类型的参数 AnyObject ; 它只能保存引用(类)类型,而 UInt32 是值类型。

    另一个令人困惑的问题是,我们通常习惯于 任何对象 类型可以, 看似 持有 Int 类型,实际上这样的赋值隐式转换Swift本机 国际 基础的值类型 __NSCFNumber 引用类型。但是,此隐式转换不适用于 UInt32 类型

    var a : AnyObject?
    let foo : [Int] = [1, 2, 3]
    let bar : [UInt32] = [1, 2, 3]
    
    /* OK: Int -> [implicitly] -> __NSCFNumber */
    a = foo[0]
    print(a!.dynamicType) // __NSCFNumber
    
    /* Not OK */
    a = bar[0]
    /* error: cannot subscript a value of type '[UInt32]' a = bar[0] */
    

    因此,您可以通过以下方式解决此问题:

    1. 出租 selectedNumbers 是数组0f 国际 而不是 UInt32 (并相应地修改代码中受影响的部分)。

    2. 从执行类型转换 UInt32 国际 在您的呼叫中 .queryEqualToValue(..) 例如,在上面的示例中:

      a = Int(bar[0])
      

      请注意,对于32位系统(如iPhone 5) UInt32 类型不能由表示 国际 类型,因为在32位系统上, 国际 对应于 Int32 .

      INT32_MAX   // 2147483647
      UINT32_MAX  // 4294967295
      

      然而,从代码的快速浏览来看,这似乎不应该是一个问题,因为 选定的号码 不会包含由 UInt32 (和,对于64位系统:OK,as 国际 对应于 Int64 ). 但是,如果选择此选项,为了良好的实践,您应该在转换之前断言 UInt32 值可以由 国际 键入要运行应用程序的系统。