在 NSUserDefaults 中存储 [String]

Question

我想将 Swift 样式字符串数组保存到 NSUserDefaults 中，但实际上代码中的“if”语句表明 returnValue 始终为 nil。

稍后在代码中 (iOS 8) 我想使用 "food += ["spaghetti"] 添加新条目。

var food : [String] {
    get {
        var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
        if returnValue == nil      //Check for first run of app
        {
            returnValue = ["muesli", "banana"]; //Default value
        }
        return returnValue!
    }
    set (newValue) {
        NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
        NSUserDefaults.standardUserDefaults().synchronize()
    }
}

Answer 1

以下代码应该可以帮助您解决问题：

import UIKit

class ViewController: UIViewController {

    var food: [String] {
        get {
            if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
                return returnValue
            } else {
                return ["muesli", "banana"] //Default value
            }
        }
        set {
            NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
            NSUserDefaults.standardUserDefaults().synchronize()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        print(food) // prints: ["muesli", "banana"] (at first launch)

        food = ["cake"]
        print(food) // prints: ["cake"]

        food += ["spaghetti"]
        print(food) // prints: ["cake", "spaghetti"]

        food = []
        print(food) // prints: []

        NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
        print(food) // prints: ["muesli", "banana"]
    }

}

---

但是，对于前面的代码，如果您设置food = []，您将遇到问题，因为food 不会返回["muesli", "banana"]。为了避免这种情况，您可能更喜欢以下代码：

import UIKit

class ViewController: UIViewController {

    var food: [String] {
        get {
            if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
                return returnValue == [] ? ["muesli", "banana"] : returnValue
            } else {
                return ["muesli", "banana"] //Default value
            }
        }
        set {
            NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
            NSUserDefaults.standardUserDefaults().synchronize()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        print(food) // prints: ["muesli", "banana"] (at first launch)

        food = ["cake"]
        print(food) // prints: ["cake"]

        food += ["spaghetti"]
        print(food) // prints: ["cake", "spaghetti"]

        food = []
        print(food) // prints: ["muesli", "banana"]

        NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
        print(food) // prints: ["muesli", "banana"]
    }

}

Answer 2

如documentation中所述：

对于 NSArray 和 NSDictionary 对象，它们的内容必须是属性 列出对象。

这意味着您需要在保存时将 String 对象转换为 NSString，这样应该可以工作：

var food : [String] {
    get {
        var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
        if returnValue == nil      //Check for first run of app
        {
            returnValue = ["muesli", "banana"]; //Default value
        }
        return returnValue!
    }
    set (newValue) {
        //  Each item in newValue is now a NSString
        let val = newValue as [NSString]
        NSUserDefaults.standardUserDefaults().setObject(val, forKey: "food")
        NSUserDefaults.standardUserDefaults().synchronize()
    }
}

Answer 3

在 Swift 3.0 中

商店

UserDefaults.standard.set(newValue, forKey: "yourkey")
UserDefaults.standard.synchronize()

检索

var returnValue: [NSString]? = UserDefaults.standard.object(forKey: "yourkey") as? [NSString]

删除

UserDefaults.standard.removeObject(forKey: "yourkey")

参考：NSUserdefault objectTypes

Answer 4

使用函数设置和获取 NSUserDefault

使用下面的函数全局使用，在任何类中声明任何在整个应用程序中的使用

声明n

func setUserDefault(ObjectToSave : AnyObject?  , KeyToSave : String)
{
    let defaults = NSUserDefaults.standardUserDefaults()

    if (ObjectToSave != nil)
    {

        defaults.setObject(ObjectToSave, forKey: KeyToSave)
    }

    NSUserDefaults.standardUserDefaults().synchronize()
}

func getUserDefault(KeyToReturnValye : String) -> AnyObject?
{
    let defaults = NSUserDefaults.standardUserDefaults()

    if let name = defaults.valueForKey(KeyToReturnValye)
    {
        return name
    }
    return nil
}

如何拨打电话

Classname_where_this_function_declare.sharedInstance.setUserDefault("value", KeyToSave: "key")**  

Answer 5

//

    class func saveCustomObject(_ object: AnyObject?, key: String) { 
      let encodedObject = NSKeyedArchiver.archivedData(withRootObject: object!) 
      let userDefaults = UserDefaults.standard userDefaults.set(encodedObject, forKey: key) 
      userDefaults.synchronize() 
    } 

//

class func loadCustomObject(_ key: String) -> AnyObject? { 
   let userDefaults = UserDefaults.standard 
   if let userDefaultKey = userDefaults.object(forKey: key) { 
     let encodedObject = userDefaultKey as! NSData 
     return NSKeyedUnarchiver.unarchiveObject(with: encodedObject as Data)! as AnyObject? 
   } else {
     return nil 
   }
} 

//

class func removeCustomObject(_ key: String) { // 
    let encodedObject = NSKeyedArchiver.archivedDataWithRootObject(object!) let userDefaults = 
    UserDefaults.standard userDefaults.removeObject(forKey: key) 
    userDefaults.synchronize()
 }

---

调用方法

let aParams : [String : String] = [ "DeviceType" : "iOS", ]
CommonMethods.saveCustomObject(aParams as AnyObject?, key:Constants.kLoginData)

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