关于 Swift 和 Cocoa 的问题之一是使用 NSUserDefaults，因为没有类型信息并且总是需要转换 objectForKey 的结果。到你期望得到的。这是不安全和不切实际的。我决定解决这个问题，让 NSUserDefaults 在 Swift-land 中更加实用，并希望在此过程中学到一些东西。这是我一开始的目标:

struct UDKey <T>  {
    init(_ n: String) { name = n }
    let name: String
}

struct UDKeys {}

extension UDKeys {
    static let MyKey1 = UDKey<Int>("MyKey1")
    static let MyKey2 = UDKey<[String]>("MyKey2")
}

class UserDefaultsClass {
    let storage = NSUserDefaults.standardUserDefaults()
    init(storage: NSUserDefaults) { self.storage = storage }
    init() {}

    // ...
}

let UserDefaults = UserDefaultsClass() // or UserDefaultsClass(storage: ...) for further customisation

let value = UserDefaults.myMethod(...)

subscript<T: NSCoding>(key: UDKey<T>) -> T? {
    set { storage.setObject(NSKeyedArchiver.archivedDataWithRootObject(newValue), forKey: key.name) }
    get {
        if let data = storage.objectForKey(key.name) as? NSData {
            return NSKeyedUnarchiver.unarchiveObjectWithData(data) as? T
        } else { return nil }
    }
}

func set <T: NSCoding>(key: UDKey<T>, _ value: T) {
    storage.setObject(NSKeyedArchiver.archivedDataWithRootObject(value), forKey: key.name)
}
func get <T: NSCoding>(key: UDKey<T>) -> T? {
    if let data = storage.objectForKey(key.name) as? NSData {
        return NSKeyedUnarchiver.unarchiveObjectWithData(data) as? T
    } else { return nil }
}

extension UDKeys { static let MyKey = UDKey<NSNotification>("MyKey") }

UserDefaults.set(UDKeys.MyKey, NSNotification(name: "Hello!", object: nil))
let n = UserDefaults.get(UDKeys.MyKey)

A default object must be a property list, that is, an instance of (or for collections a combination of instances of): NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary.

func set <T: AnyObject>(key: UDKey<T>, _ value: T) {
    storage.setObject(value, forKey: key.name)
}
func get <T: AnyObject>(key: UDKey<T>) -> T? {
    return storage.objectForKey(key.name) as? T
}

extension UDKeys { static let MyKey = UDKey<NSData>("MyKey") }

UserDefaults.set(UDKeys.MyKey, NSData())
let d = UserDefaults.get(UDKeys.MyKey)

extension UDKeys { static let MyKey = UDKey<[NSData]>("MyKey") }
UserDefaults.set(UDKeys.MyKey, [NSData()])

extension UDKeys { static let MyKey = UDKey<[Int]>("MyKey") }
UserDefaults.set(UDKeys.MyKey, [0])

extension UDKeys { static let MyKey = UDKey<Int>("MyKey") }
UserDefaults.set(UDKeys.MyKey, 1)

func set <T: Any>(key: UDKey<T>, _ value: T)

func set <T: AnyObjectiveCObject>(key: UDKey<T>, _ value: T) {
    storage.setObject(value, forKey: key.name)
}
func get <T: AnyObjectiveCObject>(key: UDKey<T>) -> T? {
    return storage.objectForKey(key.name) as? T
}

最佳答案

我不是要吹牛，但......哦，我在开玩笑，我totally do !

Preferences.set([NSData()], forKey: "MyKey1")
Preferences.get("MyKey1", type: type([NSData]))
Preferences.get("MyKey1") as [NSData]?

func crunch1(value: [NSData])
{
    println("Om nom 1!")
}

crunch1(Preferences.get("MyKey1")!)

Preferences.set(NSArray(object: NSData()), forKey: "MyKey2")
Preferences.get("MyKey2", type: type(NSArray))
Preferences.get("MyKey2") as NSArray?

func crunch2(value: NSArray)
{
    println("Om nom 2!")
}

crunch2(Preferences.get("MyKey2")!)

Preferences.set([[String:[Int]]](), forKey: "MyKey3")
Preferences.get("MyKey3", type: type([[String:[Int]]]))
Preferences.get("MyKey3") as [[String:[Int]]]?

func crunch3(value: [[String:[Int]]])
{
    println("Om nom 3!")
}

crunch3(Preferences.get("MyKey3")!)

关于swift - Swift 中的 NSUserDefaults - 实现类型安全，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28136015/