Delete all keys from a NSUserDefaults dictionary iOS - ios

Question

I use the NSUserDefaults dictionary to store basic information such as high scores etc so that when the user closes the app data is not lost. Anyways I use:
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
to store data. If I wish to store a new high score for example then I would do:
[prefs setInteger:1023 forKey:#"highScore"];
[prefs synchronize]; //this is needed in case the app is closed.
and later if I wish to retrieve the high score I would do:
[prefs integerForKey:#"highScore"];
anyways the point is that I store a lot of other things because the NSUserDefaults enable you to store booleans, integers, objects etc. what method would I have to execute to delete all keys so that NSUserDefaults becomes like the fist time I launch the app?
I am looking for something like:
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[prefs deleteAllKeysAndObjectsInTheDictionary];
or maybe there is a way of getting all keys and I have to loop through each object but I don't know how to remove them.
EDIT:
I have tried :
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[NSUserDefaults resetStandardUserDefaults];
[prefs synchronize];
and I still am able to retrieve a high score....

Answer 1

If you have a look at the NSUserDefaults documentation you will see a method - (NSDictionary *) dictionaryRepresentation. Using this method on the standard user defaults, you can get a list of all keys in the user defaults. You can then use this to clear the user defaults:
- (void)resetDefaults {
NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];
NSDictionary * dict = [defs dictionaryRepresentation];
for (id key in dict) {
[defs removeObjectForKey:key];
}
[defs synchronize];
}

Answer 2

Shortest way to do this with the same results like in Alex Nichol's top answer:
NSString *appDomain = NSBundle.mainBundle.bundleIdentifier;
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
[[NSUserDefaults standardUserDefaults] synchronize];

Answer 3

One-liner:
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:NSBundle.mainBundle.bundleIdentifier];

Answer 4

Simple Solution
Objective C:
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
Swift 3.0 to Swift 5.0 :
if let appDomain = Bundle.main.bundleIdentifier {
UserDefaults.standard.removePersistentDomain(forName: appDomain)
}

Answer 5

Swift version:
if let bid = NSBundle.mainBundle().bundleIdentifier {
NSUserDefaults.standardUserDefaults().removePersistentDomainForName(bid)
}

Answer 6

+ (void) resetStandardUserDefaults doesn't persist the changes, it simply resets the in-memory user defaults object so that the next synchronize call will read from the on-disk copy, instead of overwriting existing in-memory values with the on-disk versions.
Iterating over the keys is better, but there's actually a function that does this for you: removePersistentDomainForName:.
// you can usually get the domain via [[NSBundle mainBundle] bundleIdentifier]
[[NSUserDefaults standardUserDefaults]
removePersistentDomainForName:[[NSBundle mainBundle] bundleIdentifier]];
// or use a string for any other settings domains you use
//[[NSUserDefaults standardUserDefaults]
// removePersistentDomainForName:#"com.mycompany.myappname"];
[[NSUserDefaults standardUserDefaults] synchronize];
At the end of the synchronize operation, both the disk and memory copies of user defaults will contain none of the values set by your application.

Answer 7

Oneliner in Swift:
Swift 3
NSUserDefaults.standardUserDefaults().removePersistentDomainForName(
NSBundle.mainBundle().bundleIdentifier!)
Swift 4
UserDefaults.standard.removePersistentDomain(forName: Bundle.main.bundleIdentifier!)

Answer 8

For those of you that want to do this in the test target, use this (as the removePersistentDomain does not work for that case)
Swift 3:
for key in Array(UserDefaults.standard.dictionaryRepresentation().keys) {
UserDefaults.standard.removeObject(forKey: key)
}

Answer 9

For Swift 3:
let appDomain = Bundle.main.bundleIdentifier!
UserDefaults.standard.removePersistentDomain(forName: appDomain)

Answer 10

For Swift 3:
if let bundle = Bundle.main.bundleIdentifier {
UserDefaults.standard.removePersistentDomain(forName: bundle)
}

Answer 11

I found it the most handy to place the code in an extension on UserDefaults.
Swift 5
extension UserDefaults {
static func clear() {
guard let domain = Bundle.main.bundleIdentifier else { return }
UserDefaults.standard.removePersistentDomain(forName: domain)
UserDefaults.standard.synchronize()
}
}
Usage
UserDefaults.clear()

Answer 12

Swift
place in your logic
if let appDomain = Bundle.main.bundleIdentifier {
UserDefaults.standard.removePersistentDomain(forName: appDomain)
}

Answer 13

Swift
func resetUserDefaults(){
let userDefaults = NSUserDefaults.standardUserDefaults()
let dict = userDefaults.dictionaryRepresentation() as NSDictionary
for key in dict.allKeys {
userDefaults.removeObjectForKey(key as! String)
}
userDefaults.synchronize()
}

Answer 14

Does this method not do that:
+ (void)resetStandardUserDefaults
From the documentation for NSUserDefaults:
resetStandardUserDefaults
Synchronizes any changes made to the shared user defaults object and
releases it from memory.
+ (void)resetStandardUserDefaults
Discussion
A subsequent invocation of standardUserDefaults creates a new shared
user defaults object with the standard search list.
Based on this, you can do:
[NSUserDefaults resetStandardUserDefaults];
[NSUserDefaults standardUserDefaults];
and now the defaults should be reset.

Answer 15

Swift 3 or 4
We can even simplify described snippet into this modern expression:
func clearAll() {
let settingsDictionary = userDefaults.dictionaryRepresentation()
settingsDictionary.forEach { key, _ in userDefaults.removeObject(forKey: key) }
userDefaults.synchronize()
}

Answer 16

To remove all UserDefault value in swift (Latest syntax)
//remove UserDefaults
if let identifier = Bundle.main.bundleIdentifier {
UserDefaults.standard.removePersistentDomain(forName: identifier)
UserDefaults.standard.synchronize()
}

Answer 17

In Swift 5.0 below single line of code is enough.
UserDefaults.standard.dictionaryRepresentation().keys.forEach(defaults.removeObject(forKey:))

Answer 18

I use this:
UserDefaults.standard.removeAll()