Sharing the implementation method of a stopwatch app on iOS

- (IBAction) startOrstop:(UIButton *)sender 
{ 
//Click the background image of the toggle button
    UIImage *newImage = (checked) ? [UIImage imageNamed:@""] : [UIImage imageNamed:@""]; 
    [leftBtn setBackgroundImage:newImage forState:UIControlStateNormal]; 
     
    NSString *titlel = (checked) ? (@"Stop") : (@"Start"); 
    [leftBtn setTitle:titlel forState:UIControlStateNormal]; 
    NSString *titler = (checked) ? (@"Lap") : (@"Reset"); 
    [rightBtn setTitle:titler forState:UIControlStateNormal]; 
   
       
    if (checked)   //start 
    { 
        timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(updateTime) userInfo:nil repeats:YES]; 
    }else {        //stop 
        [timer invalidate]; 
    } 
     
    checked = !checked; 
} 
 
- (IBAction) resetOrLap:(UIButton *)sender 
{ 
    static NSInteger count = 1; 
     
    if (checked) //reset 
    { 
        time = time_lap = 0.0; 
        timestr = [NSString stringWithFormat:@"00:00.0"]; 
        [label setText:timestr]; 
        list_time = list_lap = nil; 
        count = 1; 
        [tableview reloadData]; 
         
    }else {      //lap 
        if (list_time == nil) { 
            list_time = [[NSArray alloc]initWithObjects:timestr_lap, nil]; 
            list_lap = [[NSArray alloc]initWithObjects:[NSString stringWithFormat:@"%d",count++], nil]; 
        }else { 
#if 0 
            [list arrayByAddingObject:timestr]; 
#else 
            NSArray *array = [[NSArray alloc]initWithObjects:timestr_lap, nil]; 
            list_time = [array arrayByAddingObjectsFromArray:list_time]; 
            array = [[NSArray alloc]initWithObjects:[NSString stringWithFormat:@"%d",count++], nil]; 
            list_lap = [array arrayByAddingObjectsFromArray:list_lap]; 
#endif 
        } 
        time_lap = 0; 
        [tableview reloadData]; 
     } 
} 
 
- (float) updateTime 
{ 
    time+=0.1; 
    time_lap +=0.1; 
    timestr = [NSString stringWithFormat:@"%02d:%04.1f",(int)(time / 60) ,time - ( 60 * (int)( time / 60 ) )]; 
    timestr_lap = [NSString stringWithFormat:@"%02d:%04.1f",(int)(time_lap / 60) ,time_lap - ( 60 * (int)( time_lap / 60 ) )]; 
    [label setText:timestr]; 
    return time; 
} 
 
 
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{ 
    return [list_time count]; 
} 
 
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    static NSString *tableViewIdentifier = @"tableViewIdentifier"; 
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:tableViewIdentifier]; 
    if (cell == nil) { 
        cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:tableViewIdentifier];  
    } 
     
    NSUInteger row = [indexPath row]; 
     
    = [list_time objectAtIndex:row]; 
    = [UIColor blackColor]; 
    = [UIFont boldSystemFontOfSize:25.0]; 
    = UITextAlignmentCenter; 
     
    NSString *text = [[NSString alloc]initWithFormat:@"lap %@", [list_lap objectAtIndex:row]]; 
    = text; 
    return cell; 
}