Swift NSUserDefaults不保存字典？

问题描述

我有以下测试代码：

  func testSaveDictionary() {
    let userDefaults = NSUserDefaults.standardUserDefaults()
    var jo = [
      "a" : "1.0",
      "b" : "2.0"
    ]

    let akey = "aKey"
    userDefaults.setObject(jo, forKey: akey)
    var isOk = userDefaults.synchronize()

    var data0 = userDefaults.dictionaryForKey(akey)
    println(data0)

  }

println（data0）的输出为零。

The output of println(data0) is nil.

我的代码有什么问题吗？ Swift Dictionary是否现在或在最终版本中被列为属性列表？

Anything wrong with my code? Is Swift Dictionary considered property list now or in the final release?

推荐答案

更新 Swift 2，Xcode 7： / strong>由于@atxe注意到，NSUserDefaults字典现在映射为 [String，AnyObject] 。这是Objective-C轻量级泛型的
结果，它允许
将Objective-C方法声明为

Update for Swift 2, Xcode 7: As @atxe noticed, NSUserDefaults dictionaries are now mapped as [String, AnyObject]. This is aconsequence of the Objective-C "lightweight generics" which allowto declare the Objective-C method as

- (NSDictionary<NSString *,id> *)dictionaryForKey:(NSString *)defaultName

（默认对象必须是属性列表，特别是字典
键只能是字符串。）

(Default objects must be property lists and in particular the dictionarykeys can only be strings.)

另一方面，Swift字典被桥接如果可能的话可以自动进行，所以来自问题的原始代码工作（再次）：

On the other hand, a Swift dictionary is bridged automatically if possible, so the original code from the question works (again):

let jo = [
    "a" : "1.0",
    "b" : "2.0"
]

let akey = "aKey"
// Swift 2:
userDefaults.setObject(jo, forKey: akey)
// Swift 3:
userDefaults.set(jo, forKey: akey)

---

Swift 1.2的原始答案
用户默认值可以存储 NSDictionary 对象。这些映射到Swift
作为 [NSObject：AnyObject] ：

---

Original answer for Swift 1.2:The user defaults can store NSDictionary objects. These are mapped to Swiftas [NSObject : AnyObject]:

var jo : [NSObject : AnyObject] = [
    "a" : "1.0",
    "b" : "2.0"
]
userDefaults.setObject(jo, forKey: akey)
var isOk = userDefaults.synchronize()

请注意， code> dictionaryForKey（）返回一个可选项，所以你应该检查一下
，例如可选的分配：

And note that dictionaryForKey() returns an optional, so you should check itfor example with an optional assignment:

if let data0 = userDefaults.dictionaryForKey(akey) {
    println(data0)
} else {
    println("not set")
}

// Output: [b: 2.0, a: 1.0]

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