CODEWITHSUNDEEP
objective-ccocoanstimer
JDanek
JDanek

Reputation: 49

Decreasing NSTimer interval every time it runs

I want my NSTimer to speed up each time it's run:

-(void)runtimer {
   int delay = delay - 1;
   [NSTimer scheduledTimerWithTimeInterval:(delay) 
                                    target:self 
                                  selector:@selector(timerTriggered:) 
                                  userInfo:nil 
                                   repeats:YES];

}

But this doesn't work. How can I make the delay keep getting smaller and smaller?

Upvotes: 0

Views: 1057

Answers (4)

Yang Meyer
Yang Meyer

Reputation: 5699

I needed this myself and wrote a component CPAccelerationTimer (Github):

[[CPAccelerationTimer accelerationTimerWithTicks:20
    totalDuration:10.0
    controlPoint1:CGPointMake(0.5, 0.0) // ease in
    controlPoint2:CGPointMake(1.0, 1.0)
    atEachTickDo:^(NSUInteger tickIndex) {
        [self timerTriggered:nil];
    } completion:^{
        [self timerTriggered:nil];
    }]
run];

This calls -timerTriggered: 20 times, spread out over 10 seconds, with ever-decreasing delays (as specified by the given Bézier curve).

Upvotes: 3

jscs
jscs

Reputation: 64002

Every time this method is run, you make a new variable called delay, then try to set it to itself minus 1. This is Undefined Behavior (the variable was not initialized to anything), and is likely to result in a garbage value for delay.*

You need to store the delay in an instance variable.

- (void) runTimer {
    // You are declaring a new int called |delay| here.
    int delay = delay - 1;
    // This is not the same |delay| that you have declared in your header.
    // To access that variable, use:
    delay = delay - 1;

*A sinus infestation by evil-aligned supernatural beings is also a possibility.

Upvotes: 1

EmilioPelaez
EmilioPelaez

Reputation: 19884

You have to declare the delay somewhere, like in the class interface or as a static variable.

Also, create a new timer every time, instead of having it repeat.

int delay = INITIAL_DELAY;

-(void)runtimer{
    [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)(delay--) target:self selector:@selector(runTimer:) userInfo:nil repeats:NO];
}

Upvotes: 0

jbat100
jbat100

Reputation: 16827

You cannot change the fire interval of the timer once you have created it. If you want a different interval you must invalidate the previous timer (hence you should keep a reference to it), and create a new timer with a different interval.

Upvotes: 0

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