Swift 词典已满但仍为空

Question

我在一个问题上坐了太久了，我真的不明白为什么会这样。我在网上搜索了解决方案，并且尝试了每一个解决方案，但仍然遇到这个问题。我在 Swift 中初始化了一个字典，然后向其中添加了一些值，但是在我添加 keys/values 之后，字典立即为空（在调试模式下检查），稍后在代码中也为 nil当试图从中读取时。这是我当前的代码：

我首先获取要添加字典的 plist：

var path = NSBundle.mainBundle().pathForResource("Questions", ofType: "plist")
var dict = NSDictionary(contentsOfFile: path!)!
var questionsArr = dict.objectForKey("Math") as NSArray
var questionsMutableArray:NSMutableArray = questionsArr.mutableCopy() as NSMutableArray

然后我创建值并将其添加到我的字典

//I have also tried with this and got the same result: var newDict = Dictionary<String, String>()
var newDict = [String: String]()
newDict["Question"] = "What is 1+1"
newDict["A"] = "One"
newDict["B"] = "Two"
newDict["C"] = "Three"

newDict 在调试模式下似乎是空的。然后我把字典写到我的 plist:

questionsMutableArray.addObject(newDict)
questionsMutableArray.writeToFile(path!, atomically: true)

稍后在代码中，我得到了这样的 plist（在我没有添加 newDict 之前它起作用了：

var path = NSBundle.mainBundle().pathForResource("Questions", ofType: "plist")
var dict = NSDictionary(contentsOfFile: path!)!

在最后一行 (NSDictinoary(contentsOfFile:path!)! 我得到这个错误：

fatal error: unexpectedly found nil while unwrapping an Optional value

有谁知道为什么会这样？帮助将不胜感激！

编辑 4)

中的解决方案

1. I'm getting an array of dictionaries from my plist (Questions).
2. I add a new dictionary to my array of dictionaries.
3. I write/save it to the plist.
4. I get the array from the plist again and investigate the content of it.
5. The new dictionary I just added is not there.

这是代码：

1) questionsArr 为空

var bundlepath:NSString = NSBundle.mainBundle().pathForResource("Questions", ofType: "plist")!

        var dict = NSMutableDictionary(contentsOfFile: bundlepath)!
        var questionsArr = dict.objectForKey("Math") as NSArray
        var questionsMutableArray:NSMutableArray = questionsArr.mutableCopy() as NSMutableArray

2) questionsMutableArray 是空的，现在里面有新问题。

var newDict = [String: String]()
    newDict["QuestionTitle"] = "What is 1+1?"
    newDict["A"] = "One"
    newDict["B"] = "Two"
    newDict["C"] = "Three"

let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
var path:NSString = documentsPath.stringByAppendingPathComponent("Questions.plist");

questionsMutableArray.addObject(newDict)
dict["Math"] = questionsMutableArray

3)

let didItSave = dict.writeToFile(path, atomically: true)

4) questionsArr 还是空的。如果我使用 'path' 而不是 'bundlepath' 就可以了！

dict = NSMutableDictionary(contentsOfFile: bundlepath)! //<- I USED 'path' INSTEAD OF 'bundlepath' and now it works!
    questionsArr = dict.objectForKey("Math") as NSArray

Answer 1

你的 plist 文件是一个字典数组，所以当你检索它时，你必须将它检索为一个 NSArray，然后将它转换为一个 Dictionary<String, String>

的数组

let array = NSArray(contentsOfFile: NSBundle.mainBundle().pathForResource("Questions", ofType: "plist")!) as [[String: String]]

然后您使用以下方法访问此数组中的特定词典：

let someDict = array[someIndex]

Answer 2

编辑了我的回答：

您正在使用以下行保存数组

questionsMutableArray.writeToFile(path!, atomically: true)

但随后尝试将其作为字典加载。您应该将问题数组设置为字典的 "Math" 键，然后像这样保存字典本身以使您的读写兼容。

dict["Math"] = questionsMutableArray 
dict.writeToFile(path!, atomically: true)

Answer 3

您正在尝试编写 iOS 捆绑包。 iOS 包是只读的，你不能写。

我建议你写在Document目录试试这个

 var bundlepath:NSString= NSBundle.mainBundle().pathForResource("Questions", ofType: "plist")

    var dict = NSDictionary(contentsOfFile: bundlepath)!
    var questionsArr = dict.objectForKey("Math") as NSArray
    var questionsMutableArray:NSMutableArray = questionsArr.mutableCopy() as NSMutableArray


    //I have also tried with this and got the same result: var newDict = Dictionary<String, String>()
    var newDict = [String: String]()
    newDict["Question"] = "What is 1+1"
    newDict["A"] = "One"
    newDict["B"] = "Two"
    newDict["C"] = "Three"

    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
    var path:NSString = documentsPath.stringByAppendingPathComponent("Questions.plist");



questionsMutableArray.addObject(newDict)

//将数组赋值回字典。字典["Math"]=questionsMutableArray

dict.writeToFile(path!, atomically: true)

    var dictFromDisk = NSDictionary(contentsOfFile: path)!

Answer 4

首先当你检索 plist 时，将它检索到一个 NSMutableDictionary

var dict = NSMutableDictionary(contentsOfFile: path!)!

然后，一旦你创建了你的数组，将你的字典 Math 键设置为它。

dict["math"] = questionsMutableArray

然后把字典写回你的路径。可能想看看它是否有效，writeToFile returns a bool.

let didItSave = dict.writeToFile(path!, atomically: true)

Swift 词典已满但仍为空

Swift Dictionary filled but still empty

xcode

dictionary

ios

swift