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Asked: 2026-05-24T11:21:30+00:00

In reference to the following question: iPhone: How do I detect when an app

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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.

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1 Answer

  1. Editorial Team

    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.

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