Swift：未知错误 - 意外地发现零，同时展开一个可选值

Question

我知道这是一个常见的错误，人们在这里发布，但我找不到与我在做什么相匹配的帖子，即使它从根本上相同。我对Swift很陌生，只是试图找到我的方式，谢谢。

我第一次打开我的应用程序，一个从MYSQL数据库读取的博客阅读器应用程序，它可以按照预期工作，我可以关注我选择和取消关注的博客。当我关注博客/单元格时，它会使用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该应用程序时，它会崩溃。

蹊跷的事情在我的loadUserDefaults因为我设置断点和崩溃，在这条线self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "followedID")!)

我知道我有一个可选的，但为什么会崩溃/回来了零，如果我有saveUserDefaults救了它。它不是储蓄吗？或者我没有正确加载它？

的错误是这样

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负责处理所有的博客对象和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

我以前File Manager保存我的归档阵列，这是最好的选择，非常简单简单。使用Swift 3。感谢@GuyKogus，@ Paulw11 & @MartinR

用它来保存我的对象

NSKeyedArchiver.archiveRootObject(myObject, toFile: filePath) 

用于放置我的对象

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

    myObject = myFollowedList 
}