How to update label once a day? - ios

Question

I'd like to have a label in my app that gets updated once a day at a specific time (i.e. 12 a.m.). If you could help me out I'd really appreciate it, thanks.
This is what i currently have but it only works if the app is opened between 12 and 1 am.
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:#"HH"];
NSString *stringDate = [formatter stringFromDate:[NSDate date]];
if ([stringDate isEqualToString:#"00"]) {
NSLog(#"its working");
[self changeLabel];
}
To clarify, I'm trying to change the text of a label once a day. I'd like to have the label update at a specific time like 12 am so that it updates with the start of each new day. I've tried a few ways of doing this but haven't gotten the desired result. If anyone knows of a way to do this I'd appreciate your input.

Answer 1

If you only need to determine the last time the application was opened, you can use NSUserDefaults to save the date and then check that the approprate number of seconds (86400 = 1 day) have passed.
Something along the lines of the following should point you in the right direction:
//gather last time app was opened
NSDate *lastUpdated = [[NSUserDefaults standardUserDefaults] objectForKey:#"app_last_updated"];
//check date is valid
if(lastUpdated)
{
//determine number of seconds that have passed
NSTimeInterval timeInterval = [lastUpdated timeIntervalSinceNow];
//check time interval is greater than 1 day
if(timeInterval > 86400)
{
//update label
}
}
//save current time
[[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:#"app_last_updated"];

Answer 2

It depends on what you want to do. On iOS, most likely your app is not running in the foreground all the time. So I would just update the label when the application is active in applicationDidBecomeActive:. Then I would create a timer to fire at the specific date/time I want.
For example:
NSDate *d = // create the next date/time
updateTimer_ = [[NSTimer alloc] initWithFireDate: d
interval: 0
target: self
selector:#selector(updateLabel:)
userInfo:nil repeats:NO];
NSRunLoop *runner = [NSRunLoop currentRunLoop];
[runner addTimer:updateTimer_ forMode: NSDefaultRunLoopMode];

Answer 3

I know this is an old post but a few days ago I needed just what Dave123 asked and I came up with this solution after searching a lot on the web:
- (void)applicationDidBecomeActive:(UIApplication *)application {
NSLog(#"applicationDidBecomeActive");
self.masterviewController = [[PBMasterViewController alloc] init];
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
NSLog(#"Seconds --------> %.f",[[NSDate date] timeIntervalSinceDate:[[NSUserDefaults standardUserDefaults] objectForKey:#"OLD_DATE"]]);
NSLog(#"old date: %#", [[NSUserDefaults standardUserDefaults] objectForKey:#"OLD_DATE"]);
// 24 hours must elapse between each update check
if ([[NSDate date] timeIntervalSinceDate:[[NSUserDefaults standardUserDefaults] objectForKey:#"OLD_DATE"]] > 86400) {
NSLog(#"Time elapsed since last update is MORE than 1 day. Check for updates.");
[self.masterviewController checkForUpdates];
} else {
NSLog(#"Time elapsed since last update is LESS than 1 day. Don't check for updates.");
}
// Here I convert the seconds into hours with two decimals, if you want to show the time elapsed in a UILabel
NSString *stringCheckInterval = [NSString stringWithFormat:#"%.02f hours since last update", [[NSDate date] timeIntervalSinceDate:[[NSUserDefaults standardUserDefaults] objectForKey:#"OLD_DATE"]] / 60 / 60];
NSLog(#"%#", stringCheckInterval);
}

Answer 4

is there someone that has the app opened form more than 24h??
Anyway, you can simply use an NSTimer with 86400 as delay time.

Answer 5

When you start the app, set up a timer that will fire at 12:00:01 AM and update your label.