Question

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How to make a periodic call to a method in objective c?

I am making an app where when the user touches the screen, the following method is called:

- (void)explode:(int)x

The user only has to touch the screen once, but I want the method to be called repeatedly every 0.1 seconds for 100 times, and then it should stop being called.

Is there a way of setting up a ‘temporary’ timer like this on a method where an integer is being passed?

Answer 1

You could pass a counter and the ‘x’ as into the timer’s userInfo. Try this:

Create the timer in the method that’s catching the touch event and pass a counter and the int ‘x’ into the userInfo:

NSMutableDictionary *userInfo = [[NSMutableDictionary alloc] initWithCapacity:2];
[userInfo setValue:[NSNumber numberWithInt:x] forKey:@"x"];
[userInfo setValue:[NSNumber numberWithInt:0] forKey:@"counter"];

[NSTimer timerWithTimeInterval:0.1
                        target:self
                      selector:@selector(timerMethod:)
                      userInfo:userInfo
                       repeats:YES];

Create the timer method, check the userInfo’s number count, and invalidate the timer after 100 times:

- (void)timerMethod:(NSTimer *)timer
{
    NSMutableDictionary *userInfo = timer.UserInfo;
    int x = [[userInfo valueForKey:@"x"] intValue];

    // your code here

    int counter = [[userInfo valueForKey:@"counter"] intValue];
    counter++;

    if (counter >= 100)
    {
        [timer invalidate];
    }
    else
    {
        [userInfo setValue:[NSNumber numberWithInt:x] forKey:@"x"];
        [userInfo setValue:[NSNumber numberWithInt:counter] forKey:@"counter"];
    }

}

Please also see the Apple docs on NSTimer:

https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/nstimer_Class/Reference/NSTimer.html