Swift：未知错误 - 在展开可选值时意外发现 nil

Question

我知道这是人们 post 的一个常见错误，但我找不到 post 与我正在做的事情相匹配，即使它在根本上是相同的。我是 Swift 的新手，正在努力寻找自己的出路，谢谢。

我第一次打开我的应用程序，一个从 MYSQL 数据库读取的博客 reader 应用程序，它按预期工作，我可以关注我选择的博客和取消关注。当我跟随 blog/cell 时，它使用 KeyArchiver 保存到用户默认值，但是当我双击主页按钮以从内存中清除应用程序并重新打开应用程序时，它崩溃了。

我的 loadUserDefaults 出了点问题，因为我设置了断点，它在这一行崩溃了 self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "followedID")!)

我知道我有一个可选的，但如果我用 saveUserDefaults 保存它，为什么它会崩溃/返回 nil。不节省吗？还是我加载不正确？

错误是这样的

fatal error: unexpectedly found nil while unwrapping an Optional value

代码：这是MainController.swift

var mainArray = [Blog]()
var followedArray = [Blog]()
var filteredArray = [Blog]()
var followedIdentifiers = Set<String>()

override func viewDidLoad() {
    super.viewDidLoad()

    // Receiving Data from Server
    retrieveDataFromServer()

    // NSCoding - Unarchiving Data (followedID)
    loadUserDefaults()
}

// NSCoding: Archiving UserDefaults
func saveUserDefaults() {

    // Saving to UserDefaults
    let encodedData = NSKeyedArchiver.archivedData(withRootObject: self.followedIdentifiers)
    UserDefaults.standard.setValue(encodedData, forKey: "followedID")
    UserDefaults.standard.synchronize()
}

// NSCoding: Unarchiving UserDefaults
func loadUserDefaults() { // --- Crash is Here ---

    // Unarchiving Data
    if let data = UserDefaults.standard.data(forKey: "followedID"), let myFollowedList = NSKeyedUnarchiver.unarchiveObject(with: data) as? Set<String> {

        self.followedIdentifiers = myFollowedList
        self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "followedID")!) // CRASH

    } else {
        print("Error/ Empty: (Loading UserDefaults (followedID))")
    }
}

// Retrieving Data from Server
func retrieveDataFromServer() {

    let getDataURL = "http://example.com/receiving.php"
    let url: NSURL = NSURL(string: getDataURL)!

    do {
        let data: Data = try Data(contentsOf: url as URL)
        let jsonArray = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! NSMutableArray

        // Clear the arrays
        self.followedArray = [Blog]()
        self.mainArray = [Blog]()

        // Looping through jsonArray
        for jsonObject in jsonArray {

            if let blog = Blog(jsonObject:jsonObject as! [String : Any]) {

                // Check if identifiers match
                if followedIdentifiers.contains(blog.blogID) {
                    self.followedArray.append(blog)
                } else {
                    self.mainArray.append(blog)
                }
            }
        }
    } catch {
        print("Error: (Retrieving Data)")
    }
    myTableView.reloadData()
}

这是 Blog.swift，它处理所有博客对象和 NSCoding

class Blog: NSObject, NSCoding {

var blogName: String
var blogStatus1: String
var blogStatus2: String
var blogURL: String
var blogID: String
var blogType: String
var blogDate: String
var blogPop: String


private init (name: String,status1: String,status2: String,url: String,id: String,type: String,date: String,pop: String) {
    blogName = name
    blogStatus1 = status1
    blogStatus2 = status2
    blogURL = url
    blogID = id
    blogType = type
    blogDate = date
    blogPop = pop
    super.init()
}

convenience init?(jsonObject: [String:Any]) {

    guard let bID = jsonObject["id"] as? String,
        let bName = jsonObject["blogName"] as? String,
        let bStatus1 = jsonObject["blogStatus1"] as? String,
        let bStatus2 = jsonObject["blogStatus2"] as? String,
        let bURL = jsonObject["blogURL"] as? String,
        let bType = jsonObject["blogType"] as? String,
        let bDate = jsonObject["blogDate"] as? String,
        let bPop = jsonObject["blogPop"] as? String

        else {
            print("Error: (Creating Blog Object)")
            return nil
    }

    self.init(name: bName, status1: bStatus1, status2: bStatus2, url: bURL, id: bID, type: bType, date: bDate, pop: bPop)

}

convenience required init?(coder aDecoder: NSCoder) {
    guard let blogName = aDecoder.decodeObject(forKey: "blogName") as? String,
        let blogStatus1 = aDecoder.decodeObject(forKey: "blogStatus1") as? String,
        let blogStatus2 = aDecoder.decodeObject(forKey: "blogStatus2") as? String,
        let blogURL = aDecoder.decodeObject(forKey: "blogURL") as? String,
        let blogID = aDecoder.decodeObject(forKey: "blogID") as? String,
        let blogType = aDecoder.decodeObject(forKey: "blogType") as? String,
        let blogDate = aDecoder.decodeObject(forKey: "blogDate") as? String,
        let blogPop = aDecoder.decodeObject(forKey: "blogPop") as? String else {
            print("Error: (Creating Blog Object)")
            return nil
    }
    self.init(name: blogName, status1: blogStatus1, status2: blogStatus2, url: blogURL, id: blogID, type: blogType, date: blogDate, pop: blogPop)
}

func encode(with aCoder: NSCoder) {
    aCoder.encode(blogName, forKey: "blogName")
    aCoder.encode(blogStatus1, forKey: "blogStatus1")
    aCoder.encode(blogStatus2, forKey: "blogStatus2")
    aCoder.encode(blogURL, forKey: "blogURL")
    aCoder.encode(blogID, forKey: "blogID")
    aCoder.encode(blogType, forKey: "blogType")
    aCoder.encode(blogDate, forKey: "blogDate")
    aCoder.encode(blogPop, forKey: "blogPop")
 }
}

Answer 1

我使用 File Manager 来保存我的存档数组，这是最好的选择，简单易行。使用 Swift 3。感谢@GuyKogus、@Paulw11 和@MartinR

用于保存我的对象

NSKeyedArchiver.archiveRootObject(myObject, toFile: filePath)

用于加载我的对象

if let myFollowedList = NSKeyedUnarchiver.unarchiveObject(withFile: filePath) as? Set<String> {

    myObject = myFollowedList
}

Swift：未知错误 - 在展开可选值时意外发现 nil

Swift: Unknown error - Unexpectedly found nil while unwrapping an Optional value

ios

swift

nsuserdefaults

optional

nskeyedarchiver