Setting initial NSUserDefaults

Question

I have seen some guides that say to do this, and others that say setting initial values and keys of NSUserDefaults this way will cause problems when an app is updated. I'm hoping I can definitively answer that here. In my appdelegate didFinishLaunchingWithOptions method I have:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    if (![defaults integerForKey:@"totalDays"]) {

        // if there is no value for the key, set it to 1
        [defaults setInteger:0 forKey:@"totalDays"];

    }
    if (![defaults objectForKey:@"currentDate"]) {
        [defaults setObject:@"32 01" forKey:@"currentDate"];
    }
    if (! [defaults boolForKey:@"marked"]) {
        [defaults setBool:NO forKey:@"marked"];

    }
    if (![defaults arrayForKey:@"checkedrows"]) {
        NSMutableArray *arr1  = [NSMutableArray arrayWithArray:[defaults arrayForKey:@"checkedrows"]];
    }
[defaults synchronize];

Also this answer might be helpful to you: http://stackoverflow.com/questions/4931167/what-is-the-use-of-nsuserdefaults-registerdefaults — Alladinian, Dec 19 '12 at 15:40

score 2 · Answer 1 · answered Dec 19 '12 at 14:20

It might also be helpful to note, you don't "need" default values in there to use them. It might save you time from having to check them for null or zero values later in the app.

As the other answer stated, once values are saved to user defaults, it should persist from update to update and backup to backup. I've been using them for years with no issues with lost or corrupted data.

score 1 · Answer 2 · answered Dec 19 '12 at 14:17

1

The data stored in the user defaults are save if the user updates the app. You will not get any problems with your code after an update.

answered Dec 19 '12 at 14:17

zeiteisen

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score 1 · Answer 3 · answered Dec 29 '12 at 18:22

You should not set the default values at all! Instead, use the handy method NSUserDefaults provides for exactly this purpose: -registerDefaults:. Call it early in your program's startup with a dictionary of the default values.

The advantage of this is that because -registerDefaults: is transient, you can tell the difference between "the user hasn't customized this preference" and "the user explicitly set this preference to the default value", which is important if you change default settings in a newer version of the program. It's also a little faster due to not needing to save to the disk.

Setting initial NSUserDefaults

3 Answers3