Adding two values in the strings together in ios - iphone

Question

I would like to add the values in the strings together which are in the format:"HH:mm:ss.SSS" and display it back again. In my case, it is adding timeString with difference to get currentString. I am not sure of the correct way of doing it. I am definitely doing it wrongly. The problem i face is that when i click the stop button and click start again, it starts off from 0 again.. I would like it to start off from the same spot where it left off..
The portion of the code is here:
-(void)updateTimer{
currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss.SSS"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
timeString=[dateFormatter stringFromDate:timerDate];
currentString=[dateFormatter stringFromDate:timerDate];
//double doubleOfString = [timeString doubleValue] + [difference doubleValue];
//currentString = [NSString stringWithFormat:#"%f",doubleOfString];
lbl.text = currentString;
}
The entire code is here:
Viewcontroller.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController<UITableViewDataSource,UITableViewDelegate>{
UILabel *lbl;
NSTimer *stopTimer;
NSDate *startDate,*currentDate;
BOOL running,lap;
UIButton *bttn;
NSMutableArray *tableItems;
NSString *timeString,*currentString,*difference;
UITableView *tableview;
}
#property (strong,nonatomic) IBOutlet UILabel *lbl;
#property (strong,nonatomic) IBOutlet UIButton *bttn;
#property (strong,nonatomic) NSMutableArray *tableItems;
#property (strong,nonatomic) NSString *timeString;
#property (strong,nonatomic) IBOutlet UITableView *tableview;
-(IBAction)startPressed:(id)sender;
-(IBAction)resetPressed:(id)sender;
-(void)updateTimer;
#end
ViewController.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize lbl,bttn,tableItems,timeString,tableview;
- (void)viewDidLoad
{
[super viewDidLoad];
lbl.text = #"00.00.00.000";
running = FALSE;
lap = FALSE;
difference = #"0";
startDate = [NSDate date];
tableItems = [[NSMutableArray alloc] init];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(IBAction)startPressed:(id)sender{
if(!running){
running = TRUE;
lap = TRUE;
[sender setTitle:#"Stop" forState:UIControlStateNormal];
[bttn setTitle:#"Lap" forState:UIControlStateNormal];
if (stopTimer == nil) {
stopTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0
target:self
selector:#selector(updateTimer)
userInfo:nil
repeats:YES];
}
}else{
running = FALSE;
lap = FALSE;
startDate = currentDate;
difference = currentString;
[sender setTitle:#"Start" forState:UIControlStateNormal];
[bttn setTitle:#"Restart" forState:UIControlStateNormal];
[stopTimer invalidate];
stopTimer = nil;
}
}
-(void)updateTimer{
currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss.SSS"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
timeString=[dateFormatter stringFromDate:timerDate];
currentString=[dateFormatter stringFromDate:timerDate];
double doubleOfString = [timeString doubleValue] + [difference doubleValue];
//currentString = [NSString stringWithFormat:#"%f",doubleOfString];
lbl.text = currentString;
}
-(IBAction)resetPressed:(id)sender{
if (!lap) {
[stopTimer invalidate];
stopTimer = nil;
tableItems = [[NSMutableArray alloc] init];
startDate = [NSDate date];
lbl.text = #"00.00.00.000";
running = FALSE;
}
else{
[tableItems insertObject:timeString atIndex:0];
[tableview reloadData];
}
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return tableItems.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
//Step 1:Check whether if we can reuse a cell
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"cell"];
//Step2: If there are no new cells to reuse,create a new one
if(cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:(UITableViewCellStyleDefault) reuseIdentifier:#"cell"];
//UIView *v = [[UIView alloc] init];
//v.backgroundColor = [UIColor redColor];
//cell.selectedBackgroundView = v;
//changing the radius of the corners
//cell.layer.cornerRadius = 10;
}
//Step 3: Set the cell text content
cell.textLabel.text = [tableItems objectAtIndex:indexPath.row];
//Step 4: Return the row
return cell;
}
#end
I welcome any other corrections that you can suggest...

Answer 1

I would kindly suggest not applying math to strings.
I mean:
What's the sum of the words “apple” and “Millenium Falcon”? Doesn’t make any sense, does it?
So why are you trying to form an addition of two strings, when you had a perfectly good number (timeInterval) — a type perfectly suitable to perform algebraic operations on?
PS:
NSDateFormatter instances want to be reused. Stash yours in an instance variable.

Answer 2

Your update timer function will be:Firstly add int counter in .h file . In viewDidLoad counter = 0;
-(void)updateTimer{
counter ++;
int hours = counter / 3600 ;
int minutes = (counter / 60) - (hours * 60);
int seconds = counter - (hours * 3600) - (minutes * 60);
lbl.text = [NSString stringWithFormat:#"%02d:%02d:%02d", hours, minutes, seconds];
}