Saving bool to NSUserDefaults and using it in a if statement using Swift

问题

I am struggling to figure out how to do an if statement with a bool saved to NSUserDefaults using Swift. I believe I know how to save the bool to NSUserDefaults but a confirmation in that would be greatly appreciated. This is the Objective-C code I am trying to figure out how to use with swift.

if(![[NSUserDefaults standardUserDefaults] boolForKey:@"onoroff"]) {
    [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"onoroff"];
}

this is what I have so far in Swift...

if  NSUserDefaults.standardUserDefaults().objectForKey("onoroff") != nil{
    NSUserDefaults.standardUserDefaults().setBool(false, forKey: "onoroff")
}

I think I might have figure it out. Can anyone confirm this is the correct way to save a bool to NSUserDefaults and use a if statement with it. Here it is:

if  !NSUserDefaults.standardUserDefaults().boolForKey("onoroff"){
     NSUserDefaults.standardUserDefaults().setBool(true, forKey: "onoroff")
}else{ NSUserDefaults.standardUserDefaults().setBool(false, forKey: "onoroff")
     }

回答1:

if NSUserDefaults.standardUserDefaults().boolForKey("onoroff") == true

The above code is only check wheather the value of the key is true or not.

if NSUserDefaults.standardUserDefaults().objectForKey("onoroff")

The above code check wheather the value of the key is true or not as well if there is no value for the key.(Means Nothing inserted in the UserDefault of "onoroff").

EDIT

if !NSUserDefaults.standardUserDefaults().objectForKey("onoroff")
{
     NSUserDefaults.standardUserDefaults().setBool(true, forKey: "onoroff")
}
else
{
    NSUserDefaults.standardUserDefaults().setBool(false, forKey: "onoroff")
}

回答2:

In Swift 3.0

 let defaults = UserDefaults.standard

It creates the standard defaults file and configures it if it does not exist, or open it if it does.

if !UserDefaults.standard.bool(forKey: "onoroff") {
            UserDefaults.standard.set(true, forKey: "onoroff")
     } else {
            UserDefaults.standard.set(false, forKey: "onoroff")
     }

if !defaults.standard.bool(forKey: "onoroff") {
            defaults.standard.set(true, forKey: "onoroff")
     } else {
            defaults.standard.set(false, forKey: "onoroff")
     }

Thanks you @Fred for correcting the answer:-)

回答3:

The accepted answer is correct. This is the way I like to do it (Swift 3.0):

struct Settings {

fileprivate struct Keys {
    static let soundKey = "soundKey"
}

static var sound: Bool {
    set {
        UserDefaults.standard.set(newValue, forKey: Keys.soundKey)
    }
    get {
        if UserDefaults.standard.object(forKey: Keys.soundKey) == nil {
            // Value for sound not yet set ... Setting default ...

            UserDefaults.standard.set(true, forKey: Keys.soundKey)
            return true
        }
        return UserDefaults.standard.bool(forKey: Keys.soundKey)
    }

}

}

回答4:

NSUserDefaults.standardUserDefaults().setObject(Bool(false), forKey:"onoroff")

var onoroff = NSUserDefaults.standardUserDefaults().objectForKey("onoroff") as Bool!

if (onoroff != nil && onoroff == false)
{

}

EDIT:

NSUserDefaults.standardUserDefaults().setBool(false, forKey: "onoroff")

if NSUserDefaults.standardUserDefaults().boolForKey("onoroff"){

}else{

}

回答5:

To check bool value instead of objectForKey we must use boolForKey. I find that as a mistakes in the answer you accepted

       if (NSUserDefaults.standardUserDefaults().boolForKey("onoroff")){
            NSUserDefaults.standardUserDefaults().setBool(true, forKey: "onoroff")
        }else
        {
            NSUserDefaults.standardUserDefaults().setBool(false, forKey: "onoroff")
        }

回答6:

Swift 3

This is code for the switch, that will save true or false to UserDefaults.

let defaults = UserDefaults.standard
@IBOutlet weak var mySwitch: UISwitch!

@IBAction func switchValueChanged(_ sender: Any) {
    self.defaults.set(mySwitch.isOn, forKey: "mySwitch")
}

Then to show the switch's saved state... on/off:

override func viewDidLoad() {
    super.viewDidLoad() 
    mySwitch.isOn = self.defaults.bool(forKey: "mySwitch")
}

So really 1 line to set the switch's state, and 1 line to get the users saved state and set the switch properly!

来源：https://stackoverflow.com/questions/31070163/saving-bool-to-nsuserdefaults-and-using-it-in-a-if-statement-using-swift

标签

ios

xcode

swift

boolean

nsuserdefaults