Iphone app style count down improvement? - iphone

Question

I've been searching internet for a few days till now. I did find some useful information but just want to make things perfect.
I'm trying to write a countdown app which only uses second, my current code is a bit too complex and maybe off the main road. Looking for someone who can straight it up.
- (void)updateTimer{
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"s"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString=[dateFormatter stringFromDate:timerDate];
// where the part change time string back to int
NSString *changeToInt = timeString;
int stringInt = [changeToInt integerValue];
// loop for count down numbers
if ((buttValue - stringInt) > 0) {
leftTime = buttValue - stringInt;
[self updateValue];
} else {
leftTime = 0;
[self updateValue];
}
}
2 problems with the code, 1) do I have to go through all the date formatting to get a integer? 2) in the loop I used two variables, I was hoping to take one out and use something like --

Answer 1

I don't understand what you need exactly, but I think that you just want to get the number of seconds from now to a known date. The timeIntervalSinceNow method will give you a NSInteger value that represent the number of seconds from the receiver date until now, which, if the receiver is earlier than now, will be a negative value (otherwise it will be positive).
So, just to be more explicit:
- (void)updateTimer
{
leftTime = MAX(0, -[startDate timeIntervalSinceNow]); //if less than 0 will be forced to 0 -> date reached
[self updateValue];
}
As I said, I'm not sure this is what you want. If it's not, I am sorry.
Good luck!

Answer 2

-(void)initialiseTimer
{
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(timeElapsed) userInfo:nil repeats:YES];
startDate = [[NSDate date] retain];
}
-(void)timeElapsed
{
NSLog(#"Seconds elapsed since start date %d", abs([startDate timeIntervalSinceNow]));
}
you can manipulate it to make a count down style app.

Answer 3

Use this code !!
-(IBAction)startAndStop:(id)sender
{
startDate = [[NSDate date]retain];
if([btnStopWatch.titleLabel.text isEqualToString:#"Start"])
{
stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/100.0 target:self selector:#selector(updateTimer) userInfo:nil repeats:YES];
[btnStopWatch setTitle:#"Stop" forState:UIControlStateNormal];
}
else if([btnStopWatch.titleLabel.text isEqualToString:#"Stop"])
{
[stopWatchTimer invalidate];
[btnStopWatch setTitle:#"Start" forState:UIControlStateNormal];
}
}
- (void)updateTimer
{
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
timeString=[dateFormatter stringFromDate:timerDate];
stopWatchLabel.text = timeString;
NSLog(#"Seconds elapsed since start date %d", abs([startDate timeIntervalSinceNow]));
}