Remove NSUserDefaults for keys starting with

Question

I want to remove strings that are stored in the NSUserDefaults for the keys beginning with "NavView".
I thought about using the hasPrefix() method, but I just can't seem to figure it out.

I know that other programming languages have features like taking every string with a certain beginning by passing the prefix they want it to have like: find all strings with "NavView*" or something. (using signs like the star to indicate that)

Any ideas how I could do that except storing all the objects in an array and saving that?
Thanks in advance!

Answer 1

UserDefaults is one kind of key value pair persistent store. To solve your problem you have to follow the steps:

• Iterate over the all keys of UserDefaults Dictionary.
• Check each key has prefix "NavView".
• If key has the prefix then remove the object for the key.

Swift 4:

for key in UserDefaults.standard.dictionaryRepresentation().keys {
    if key.hasPrefix("NavView"){
        UserDefaults.standard.removeObject(forKey: key)
    }
}

Objective C :

NSUserDefaults *userDef = [NSUserDefaults standardUserDefaults];

for (NSString *key in [userDef dictionaryRepresentation].allKeys) {
    if ([key hasPrefix:@"start"]) {
        [userDef removeObjectForKey:key];
    }
}

Answer 2

Swift 5 is the same as Swift 4

for key in UserDefaults.standard.dictionaryRepresentation().keys {
            if key.hasPrefix("NavView") {
                UserDefaults.standard.removeObject(forKey: key)
            }
        }