CODEWITHSUNDEEP
iosswiftnsuserdefaultsoption-type
Suragch
Suragch

Reputation: 511736

How to deal with non-optional values in NSUserDefaults in Swift

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

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

However, these methods do not return optionals:

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.

How would I deal with this?

Upvotes: 4

Views: 2296

Answers (5)

vadian
vadian

Reputation: 285064

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 = UserDefaults.standard
   let defaultValues = ["key1" : 12, "key2" : 12.6]
   defaults.register(defaults: defaultValues)
   super.init()
 }

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

let defaults = UserDefaults.standard
myVariable1 = defaults.integer(forKey: "key1")
myVariable2 = defaults.double(forKey:"key2")

Upvotes: 4

Suragch
Suragch

Reputation: 511736

You can use objectForKey (which returns an optional) and use as? to optionally cast it to an Int.

if let myInteger = UserDefaults.standard.object(forKey: key) as? Int {
    print(myInteger)
} else {
    print("no value was set for this key")
}

The solutions for Bool, Float, and Double would work the same way.

Note:

I recommend going with the accepted answer and setting default values rather than casting a generic object if possible.

Upvotes: 7

Kateryna Gridina
Kateryna Gridina

Reputation: 844

This article describes very well how to "make" them Optional http://radex.io/swift/nsuserdefaults/

extension NSUserDefaults {
    class Proxy {
        var object: NSObject? {
            return defaults.objectForKey(key) as? NSObject
        }

        var number: NSNumber? {
            return object as? NSNumber
        }

        var int: Int? {
            return number?.integerValue
        }

        var bool: Bool? {
            return number?.boolValue
        }
    }
}

Upvotes: 0

Scott Berrevoets
Scott Berrevoets

Reputation: 16946

You could register defaults for your app that aren't legitimate values using NSUserDefaults.standardUserDefaults.registerDefaults()

Upvotes: 0

baydi
baydi

Reputation: 1003

Use this code 

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

Upvotes: -1

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