How do I save an Int array in Swift using NSUserDe

问题:

This is an array:

var myArray = [1]

It contains Int values.

This is how I save an array in NSUserDefaults. This code seems to be working fine:

NSUserDefaults.standardUserDefaults().setObject(myArray, forKey: "myArray")

This is how I load an array:

myArray = NSUserDefaults.standardUserDefaults().objectForKey("myArray")

The code above, though, retrieves an error. Why?

回答1:

You want to assign an AnyObject? to an array of Ints, beacuse objectForKey returns AnyObject?, so you should cast it to array this way:

myArray = NSUserDefaults.standardUserDefaults().objectForKey("myArray") as [Int]

If there are no values saved before, it could return nil, so you could check for it with:

if let temp = NSUserDefaults.standardUserDefaults().objectForKey("myArray") as? [Int] {
    myArray = temp
}

回答2:

You should use if let to unwrap your optional value and also a conditional cast. By the way you should also use arrayForKey as follow:

if let myLoadedArray = UserDefaults.standard.array(forKey: "myArray") as? [Int] {
    print(myLoadedArray)
}

Or use the nil coalescing operator ??:

let myLoadedArray = UserDefaults.standard.array(forKey: "myArray") as? [Int] ?? []

回答3:

Swift 4:

myArray : [Int] = UserDefaults.standard.object(forKey: "myArray") as! [Int]