Help changing NSTimer for textLabel. Code included - iphone

Question

want to change my NSTimer code to to use applicationSignificantTimeChange
This is what I have right now.
Basically I want to change the timer, instead of changing every 5 seconds for example I want these textLabels to change at 12am every night anyone help me out?
//h file
NSTimer *timer;
IBOutlet UILabel *textLabel;
//m file
- (void)onTimer {
static int i = 0;
if ( i == 0 ) {
textLabel.text = #"iphone app";
}
else if ( i == 1 ) {
textLabel.text = #" Great App!";
}
else if ( i == 2 ) {
textLabel.text = #" WOW!";
}
else {
textLabel.text = #" great application again!!";
i = -1;
}
i++;
}
timer =[NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:#selector(onTimer) userInfo:nil repeats:YES];

Answer 1

There are two things you can do to respond to a applicationSignificantTimeChange:
(1) Just implement applicationSignificantTimeChange: in your app delegate if you have a connection to the view controller that should be updated.
- (void)applicationSignificantTimeChange:(UIApplication *)application {
yourViewController.textLabel.text = #"random text";
}
(2) Subscribe to the UIApplicationSignificantTimeChangeNotification notification in the view controller that should get the update. You could perhaps put that code in viewDidLoad
- (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(onSignificantTimeChange:)
name:UIApplicationSignificantTimeChangeNotification
object:nil];
}
- (void)onSignificantTimeChange:(NSNotification *)notification {
self.textLabel.text = #"random text";
}
You also need to call
[[NSNotificationCenter defaultCenter] removeObserver:self];
somewhere when your view controller is not longer needed.

Answer 2

the selector for the timer should be:
-(void) onTimer:(NSTimer *) timer
{
// yourcode
}
and called with:
[NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:#selector(onTimer:) userInfo:nil repeats:YES];
you need the "onTimer*:*"
[EDIT]
for calling a function that will go off at 12:am, for low-performance (i.e. not 12:00:00:0000) you could do the following for like an app that sits in the background:
NSTimeInterval minute = 60.0f
[NSTimer scheduledTimerWithTimeInterval:minute target:self selector:#selector(onTimer:) userInfo:nil repeats:YES]
-(void) onTimer:(NSTimer *) timer
{
NSDate *midnight = [NSDate dateWithNaturalLanguageString:#"today at 12:00 am"]; // unsure of this line
if ([midnight timeIntervalSinceDate:[NSDate date]] < 30.0f)
// set off alarm.
}

Answer 3

Seems pretty straightforward to me -- just create an NSDate for midnight, calculate the time interval of 24 hours in seconds, and create the NSTimer with
- (id)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)seconds target:(id)target selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)repeats