Detecting the initial launch of an app using NSUserDefaults

Question

In reference to the following question: iPhone: How do I detect when an app is launched for the first time?

When I looked up NSUserDefaults apple reference, it said that registerDefaults does not store the data onto the disk. In the above question, the app registers the value firstLaunch to YES upon each launch. So each time the app is launched, firstLaunch is overwritten to YES and so the app will always think that this is the app's initial launch.

Am I right on this?

EDIT:

After doing what the tutorial above says, it doesn't always work anyway. I keep relaunching from Xcode and it keep printing out 1 bool value as in its the first launch.

score 5 · Accepted Answer · answered Aug 11 '11 at 10:09

registerDefaults: doesn't overwrite what is already in the defaults, but it sets defaults-for-the-defaults. So if a default is missing it uses a default-default. Confusing, isn't it?

If you've never written a value under the key FirstLaunch, then boolForKey:@"FirstLaunch" will use the value from registerDefaults:. However, if you did previously do setBool:NO forKey:@"FirstLaunch" and later ask for it again with boolForKey: then the value from registerDefaults: is not used.

score 1 · Answer 2 · answered Aug 11 '11 at 10:10

1

registerDefaults: doesn't overwrite existing values, it only initializes values that aren't set to any value yet.

answered Aug 11 '11 at 10:10

omz

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score 0 · Answer 3 · answered Aug 11 '11 at 10:04

0

Try something like this in

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

if ([[[NSUserDefaults standardUserDefaults] valueForKey:@"firstRun"] intValue]==0) {
       //do the stuff required at first launch


//after stuff done
    [[NSUserDefaults standardUserDefaults] setValue:[NSNumber numberWithInt:1] forKey:@"firstRun"];
    [[NSUserDefaults standardUserDefaults] synchronize];

    }

}

answered Aug 11 '11 at 10:04

kviksilver

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I tried all the methods - it always detects my app as a first launch! Why is that?? – darksky Aug 11 '11 at 10:15
Wow - actually yours is the only method that worked. Is it the `synchronize`? What is that – darksky Aug 11 '11 at 10:18
it is called by os periodically, but you can use it to force NSUserDefaults synchronization at that given moment – kviksilver Aug 11 '11 at 10:48

score -1 · Answer 4 · answered Aug 11 '11 at 09:31

-1

NO first it will be nil then you set it to yes and before setting it to yes check if it's already set to yes or not. So first time userDefaults will return nil if you get something for a key. like

[[NSUserDefaults standardUserDefaults] valueForKey:@"FirstLaunch"];

will return nil on first launch of application.

answered Aug 11 '11 at 09:31

Rahul Vyas

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I'm sorry but I don't understand. Your answer is not clear.. My question is, `registerDefaults:` is setting `firstLaunch` to `YES` upon each launch since its in `applicationDidFinishLaunching`. So each time this method is run, `firstLaunch` is overwritten to `YES` even though in the terminate method it is being set to `NO`. – darksky Aug 11 '11 at 09:40

Detecting the initial launch of an app using NSUserDefaults

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