How to run NSTimer until flag variable ON in Cocoa

Question

I have a problem: I want to NSTimer waiting until FLAG variable is YES, if FLAG = YES, myTimer is stop. How can i do that? I tried below code:

NSTimer *myTimer;
int delay = 6.0;
scanTimer= [NSTimer scheduledTimerWithTimeInterval:6.0 target:self selector:@selector(anotherfunc) userInfo:nil repeats:YES];
myTimer= [NSTimer timerWithTimeInterval: delay
                                         target:self
                                       selector: @selector(resetAll:) userInfo:nil
                                        repeats:NO];
        [[NSRunLoop currentRunLoop] addTimer:myTimer forMode:NSModalPanelRunLoopMode];
        [[NSApplication sharedApplication] runModalForWindow: scanningPanel];

This is resetAll () function :

-(void) resetAll: (NSTimer *) theTimer
{
    if(FLAG)
    {
        NSLog(@"killWindow");
        [[NSApplication sharedApplication] abortModal];
        [scanningPanel orderOut: nil];
        FLAG = NO;
    }
    else
    {
        delay +=6.0;
        myTimer= [NSTimer timerWithTimeInterval: delay
                                         target:self
                                       selector: @selector(resetAll:) userInfo:nil
                                        repeats:NO];
        [[NSRunLoop currentRunLoop] addTimer:myTimer forMode:NSModalPanelRunLoopMode];
        [[NSApplication sharedApplication] runModalForWindow: scanningPanel];
    }

}

I used 2 NSTimer, but only myTimer run, scanTimer not run. Please give me any suggestions. Thanks in advance

You want to end the timer as soon as the flag is raised? If that is the case you might want a timer that repeats every second or 500ms, and on each pulse check for either the flag or the duration being true. — Timothy Walters, Sep 04 '13 at 03:55
@TimothyWalters: Yes, i want to end timer as soon ass when the flag is raised. Can you example code to me? Thanks so much — Joson Daniel, Sep 04 '13 at 03:58
try without timer: http://stackoverflow.com/questions/149646/best-way-to-make-nsrunloop-wait-for-a-flag-to-be-set — stosha, Sep 04 '13 at 04:08

Brian Palma · Answer 1 · 2013-09-14T00:00:20.593

Why not use Key Value Observing for the FLAG change? Add the flag variable as a property of the class you're working in:

@property(nonatomic, assign) BOOL flag;

To avoid repetition place in your .m:

#define kFooFlagKey @"flag"

Override -setFlag: so it is KVO compliant:

-(void)setFlag:(BOOL)flag
{
    if (_flag == flag) {
        return;
    }
    [self willChangeValueForKey:kFooFlagKey];
    _flag = flag;
    [self didChangeValueForKey:kFooFlagKey];
}

In the class' initializer add self as the observer for the keypath you'd like to monitor. In this case it will be for the property "flag".

[self addObserver:self
   forKeyPath:kFooFlagKey
      options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld
      context:NULL];

Don't forget to remove the observer in the class' -dealloc:

[self removeObserver:self forKeyPath:kFooFlagKey];

Create the timer to fire repeatedly (firingCallBack is a method called with each fire):

    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.0f
                                                  target:self
                                                selector:@selector(firingCallBack)
                                                userInfo:nil
                                                 repeats:YES];

Implement KVO observing method:

-(void)observeValueForKeyPath:(NSString *)keyPath
                 ofObject:(id)object
                   change:(NSDictionary *)change
                  context:(void *)context
{
    if ([keyPath isEqualToString:kFooFlagKey]) {
        if (self.flag) {
           [self performSelector:@selector(resetAll) withObject:nil afterDelay:0.0f];
        }
    }
}

Implement -resetAll however you'd like. It will be called when you are setting the flag variable via the accessor AND the flag is set to YES

danh · Answer 2 · 2013-09-04T04:59:11.310

You just start the timer (already scheduled) and make it repeat at a relatively high frequency and stop it when the condition is met. One timer can act as two, like this:

- (void)startTimers {

    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];
}

- (void)timerFired:(NSTimer *)timer {

    if (self.stopTimerA && self.stopTimerB) {
        [timer invalidate];
    } else {
        if (!self.stopTimerA)
            [self timerAFired];
        if (!self.stopTimerB)
            [self timerBFired];
    }
}

- (void)timerAFired {
    // this can be coded like it has it's own timer
    // we didn't pass the timer, so we can't invalidate it
    // to stop...
    self.stopTimerA = YES;
}

- (void)timerBFired {
    // same idea here
}

You can use two timers, or the same timer and call two methods on the invocation. I'll add to my answer. — danh, Sep 04 '13 at 04:52

score 1 · Accepted Answer · answered Sep 04 '13 at 05:47

Try like this:-

NSTimer *myTimer;
int delay = 6.0;
scanTimer= [NSTimer scheduledTimerWithTimeInterval:6.0 target:self selector:@selector(anotherfunc) userInfo:nil repeats:YES];
myTimer= [NSTimer scheduledTimerWithTimeInterval: delay
                                         target:self
                                       selector: @selector(resetAll:) userInfo:nil
                                        repeats:NO];
[NSApp beginSheet:scanningPanel modalForWindow:[self window]
        modalDelegate:self
       didEndSelector:nil
          contextInfo:self];

- (void)resetAll:(NSTimer *)theTimer
{
    if (flag== YES)
    {
    [NSApp endSheet:scanningPanel];
    [scanningPanel orderOut:self];
        flag=NO;
    }
    else
    {
   delay +=6.0;
myTimer= [NSTimer scheduledTimerWithTimeInterval: delay
                                         target:self
                                       selector: @selector(resetAll:) userInfo:nil
                                        repeats:NO];
    [NSApp beginSheet:scanningPanel modalForWindow:[self window]
        modalDelegate:self
       didEndSelector:nil
          contextInfo:self];
    }
}

Thanks but i don't want to use beginSheet. I want to show it as NSwindow? How can i do that? — Joson Daniel, Sep 04 '13 at 06:23

How to run NSTimer until flag variable ON in Cocoa

3 Answers3