如何在Swift中处理NSUserDefaults中的非可选值 [英] How to deal with non-optional values in NSUserDefaults in Swift

问题描述

要从NSUserDefaults获取值，我将执行以下操作:

To get a value from NSUserDefaults I would do something like this:

let userDefaults = NSUserDefaults.standardUserDefaults()
if let value = userDefaults.objectForKey(key) {
    print(value)
}

但是，这些方法不返回可选值:

However, these methods do not return optionals:

• boolForKey(如果未设置，默认为false)
• integerForKey(如果未设置，默认为0)
• floatForKey(如果未设置，默认为0.0)
• doubleForKey(如果未设置，则默认为0.0)

• boolForKey (defaults to false if not set)
• integerForKey (defaults to 0 if not set)
• floatForKey (defaults to 0.0 if not set)
• doubleForKey (defaults to 0.0 if not set)

在我的应用中，我想使用整数的保存值(如果先前已设置).如果以前没有设置，我想使用自己的默认值.问题是0是我的应用程序的有效整数值，因此我无法知道0是先前保存的值还是默认的未设置值.

In my app I want to used the saved value of an integer if it has been previously set. And if it wasn't previously set, I want to use my own default value. The problem is that 0 is a valid integer value for my app, so I have no way of knowing if 0 is a previously saved value or if it is the default unset value.

我将如何处理?

推荐答案

在AppDelegate中注册用户默认值，最好的位置是awakeFromNib甚至init.您可以为每个键提供自定义默认值.

Register the user defaults in AppDelegate, the best place is awakeFromNib or even init. You can provide custom default values for every key.

 override init()
 {
   let defaults = NSUserDefaults.standardUserDefaults()
   let defaultValues = ["key1" : 12, "key2" : 12.6]
   defaults.registerDefaults(defaultValues)
   super.init()
 }

然后，您可以随时随地以非可选方式读取值

Then you can read the values from everywhere always as non-optionals

let defaults = NSUserDefaults.standardUserDefaults()
myVariable1 = defaults.integerForKey("key1")
myVariable2 = defaults.doubleForKey("key2")

这篇关于如何在Swift中处理NSUserDefaults中的非可选值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！