Question

I have created NSUserDefaults object, it will be updated with the new value whenever an even will occur.
What I want is (as per my application requirement) that object should be cleared every 7 days.
Like if 1st time that NSUserDefaults are updated today so exact after 7 days, a method should work and clear the NSUserDefaults.
So that, new values would be assigned from then on for the next 7 days.

Is it possible in objective-c?

Answer 1

What you can do is store an NSDate object. Then every time the application is launched (or more often) check if the time difference between then and now is 7 days.

const NSString *kFirstLaunchDateKey = @"firstLaunchDate";
NSDate *firstLaunchDate = [[NSUserDefaults standardUserDefaults] objectForKey:kFirstLaunchDateKey];

//  If this is the first time the app has been launched we record right now as the first time the app was launched.
if (!firstLaunchDate) {
    [[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:kFirstLaunchDateKey];
    return;
}

NSTimeInterval *diff = abs([firstLaunchDate timeIntervalSinceNow]);
if (diff > 60 * 60 * 24 * 7) {
//      Seven days have passed since the app was first launched. 
//      Display the rate button.
}

If it is call

- (void)removePersistentDomainForName:(NSString *)domainName

With your application’s bundle identifier as the parameter.

From Apple’s documentation:

domainName
The domain whose keys and values you want. This value should be equal to your application’s bundle identifier.