Check if UserDefault exists - Swift
IosSwiftNsuserdefaultsIos Problem Overview
I'm trying to check if the a user default exists, seen below:
func userAlreadyExist() -> Bool {
var userDefaults : NSUserDefaults = NSUserDefaults.standardUserDefaults()
if userDefaults.objectForKey(kUSERID) {
return true
}
return false
}
However, no mater what it will always return true even when the object doesn't exist yet? Is this the right way for checking existence ?
Ios Solutions
Solution 1 - Ios
Astun has a great answer. See below for the Swift 3 version.
func isKeyPresentInUserDefaults(key: String) -> Bool {
return UserDefaults.standard.object(forKey: key) != nil
}
Solution 2 - Ios
I copy/pasted your code but Xcode 6.1.1 was throwing some errors my way, it ended up looking like this and it works like a charm. Thanks!
func userAlreadyExist(kUsernameKey: String) -> Bool {
return NSUserDefaults.standardUserDefaults().objectForKey(kUsernameKey) != nil
}
Swift 5:
if UserDefaults.standard.object(forKey: "keyName") != nil {
//Key exists
}
Solution 3 - Ios
Yes this is right way to check the optional
have nil
or any value objectForKey
method returns AnyObject?
which is Implicit optional
.
So if userDefaults.objectForKey(kUSERID)
have any value than it evaluates to true
. if userDefaults.objectForKey(kUSERID)
has nil
value than it evaluates to false
.
From swift programming guide > If Statements and Forced Unwrapping > You can use an if statement to find out whether an optional contains a value. If an optional does have a value, it evaluates to > true; if it has no value at all, it evaluates to false.
Now there is a bug in simulators than after setting key in userDefaults
they always remain set no matter you delete your app.You need to reset simulator.
Reset your Simulator check this method before setting key in userDefaults
or remove key userDefaults.removeObjectForKey(kUSERID)
from userDefaults
and it will return NO
.On devices it is resolved in iOS8 beta4
.
Solution 4 - Ios
This is essentially the same as suggested in other answers but in a more convenient way (Swift 3+):
extension UserDefaults {
static func contains(_ key: String) -> Bool {
return UserDefaults.standard.object(forKey: key) != nil
}
}
usage: if UserDefaults.contains(kUSERID) { ... }
Solution 5 - Ios
Simple Code to check whether value stored in UserDefault.
let userdefaults = UserDefaults.standard
if let savedValue = userdefaults.string(forKey: "key"){
print("Here you will get saved value")
} else {
print("No value in Userdefault,Either you can save value here or perform other operation")
userdefaults.set("Here you can save value", forKey: "key")
}
Solution 6 - Ios
Many of the solutions here are valid. Still, I think they solve the wrong problem.
Usually, code like this is used to check if a value is set so another default value can be used:
if isKeyPresentInUserDefaults(key: "username") {
return UserDefaults.standard.string(forKey: "username")
} else {
return "No username was set"
}
You shouldn't care if a key is set or not. There is a far more elegant approach for having default values in UserDefaults
:
UserDefault.standard.register(defaults: ["username": "No username was set"])
If you run this code at app launch, subsequent calls to UserDefaults.standard.string(forKey: "username")
will return the default value of "No username was set"
if no value was set for the key yet.
Solution 7 - Ios
for swift 3.2
func userAlreadyExist(kUsernameKey: String) -> Bool {
return UserDefaults.standard.object(forKey: kUsernameKey) != nil
}
Solution 8 - Ios
public class PreferencesUtils {
private init() {
}
public static func setBoolData(boolValue: Bool, dataName: String) {
UserDefaults.standard.set(boolValue, forKey: dataName)
}
public static func getBoolData(dataName: String)-> Bool{
let defaults = UserDefaults.standard
if(defaults.value(forKey: dataName) != nil) {
return defaults.value(forKey: dataName)! as! Bool
} else {
return false
}
}
public static func saveStringData(data: String, dataName: String){
let preferences = UserDefaults.standard
preferences.set(data, forKey: dataName)
let didSave = preferences.synchronize()
if !didSave {
debugPrint("Not saved yet")
}
}
public static func getSavedStringData(dataName: String)-> String{
let defaults = UserDefaults.standard
if(defaults.value(forKey: dataName) != nil){
return defaults.value(forKey: dataName) as! String
} else {
return ""
}
}
public static func saveIntData(data : Int, dataName: String){
let preferences = UserDefaults.standard
preferences.set(data, forKey: dataName)
let didSave = preferences.synchronize()
if !didSave {
debugPrint("Not saved yet")
}
}
public static func getSavedIntData(dataName: String) -> Int {
let defaults = UserDefaults.standard
if(defaults.value(forKey: dataName) != nil){
return defaults.value(forKey: dataName) as! Int
}else{
return 0
}
}
}
Or you can try this library: Link
Solution 9 - Ios
func keyExists(key: String) -> Bool {
guard let _ = UserDefaults.standard.object(forKey: key) {
return false;
}
return true;
}
Solution 10 - Ios
override func viewDidLoad() {
super.viewDidLoad()
if UserDefaults.standard.string(forKey: "CHARRY") == "CHARRY"{
lb.text = "CHARRY"
im.image = UIImage(named: "CHARRY")
} }
@IBAction func PressedCar(_ sender: UIButton){
lb.text = "CHARRY"
im.image = UIImage(named: "CHARRY")
UserDefaults.standard.set("CAR", forKey: "CHARRY")
}