快速 valueForKeyPath 不起作用

Question

我有功能

func findObjectInArray(array: [AnyObject], field: String?, fieldValue: AnyObject, startFromTheBeginning: Bool, minIndexTemp: Int, maxIndexTemp: Int) -> AnyObject?

我有：

var minIndex = minIndexTemp
        var maxIndex = maxIndexTemp
        if (array.count == 0 || minIndex < 0 || maxIndex < 0) {
            return nil
        }
        if (minIndex > maxIndex) {
            let rem = minIndex;
            minIndex = maxIndex;
            maxIndex = rem;
        }
        if (maxIndex >= array.count) {
            maxIndex = array.count - 1;
        }
        let startIndex = startFromTheBeginning ? minIndex : maxIndex;
        let endIndex = startFromTheBeginning ? maxIndex : minIndex;

        for (var i = startIndex; (startFromTheBeginning ? i <= endIndex : i >= 0); (startFromTheBeginning ? i++ : i--)) {
            let object = array[i]
            var objectFieldValue: AnyObject? = nil
            if (field != nil) {
                print("test = ", (object as! SAd).adID)
                objectFieldValue = object.valueForKeyPath(field!)
            }

我在崩溃前记录我看到 test = 1 。所以这意味着object 被转换为SAd 并且它具有adID 字段，但是在objectFieldValue = object.valueForKeyPath(field!) 行上应用程序崩溃并出现错误：

 *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<Project.SAd 0x12d731930> valueForUndefinedKey:]: this class is not key value coding-compliant for the key adID

这里是类

class SAd: NSObject {
    var adID: Int!
    var bloggerID: Int!
    var createdOn: NSDate!
    var duration: Int!
    var fav: Int!
    var price: Double!
    var text: String!
    var countries: [String]!
    var categories: [String]!
    var deleted: Bool!
}

实际上，您可以非常简单地在代码中测试相同的行为：

创建类：

class STest: NSObject {
    var idTest: Int?
    var strTest: String?
}

在您的 AppDelegate 文件中：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    let testObj1 = STest()
    testObj1.idTest = 1
    testObj1.strTest = "test"
    let objValue = testObj1 .valueForKeyPath("idTest")

    return true
}

您将在let objValue = testObj1 .valueForKeyPath("idTest") 行看到崩溃

但如果你用let objValue = testObj1 .valueForKeyPath("strTest") 替换这一行，它会起作用。所以问题出在 Int 值上

Answer 1

您不能将 KVC 与可选的 Swift 数字结构类型一起使用，例如 Int、UInt、Float、Double 和 Bool。简单来说就是这些类型不兼容AnyObject，无法桥接。

在您的示例中，您可以使用：

var adID: NSNumber!

Answer 2

您不能将valueForKeyPath 与Optionals 一起使用。由于您将idTest 声明为可选，因此您将遇到此崩溃。试试下面的代码，它应该可以工作！

class STest: NSObject {
    var idTest: Int = 0
    var strTest: String?
}

let testObj1 = STest()
testObj1.idTest = 1
testObj1.strTest = "test"
let objValue = testObj1.valueForKeyPath("idTest") as! Int