Question

In my code, I spin a UIScrollView this way:

[carousel scrollByNumberOfItems:-35 duration:10.7550f];

[NSTimer scheduledTimerWithTimeInterval:10.7550f 
                                 target:self
                               selector:@selector(randomFinal)
                               userInfo:nil
                                repeats:NO]; 

And in this part, after the scrollView stops, it will do a random movement, either UP or Down:

-(void)randomFinal {

    randomBut = arc4random()%5;

    if (randomBut == 0){
 [carousel scrollByNumberOfItems: -1 duration: 4.50f];  
    } else if ( randomBut == 1){
 [carousel scrollByNumberOfItems: 1 duration: 4.50f];  
    } else if (randomBut == 2) {
 [carousel scrollByNumberOfItems: 1 duration: 5.0f];
    } else if (randomBut == 3) {
 [carousel scrollByNumberOfItems: -1 duration: 5.0f];
   } else if (randomBut == 4) {
 [carousel scrollByNumberOfItems:0 duration:0];
    }
}

What I need is to make the randomFinal part to happen with a percentage of 30% probability. How can I do it? thankyou.

Answer 1

You can try this:

// arc4random_uniform() returns uniformly distributed random number < than upper_bound.
randomNumber = arc4random_uniform(100 + 1);
if(randomNumber <= 30)
    do something;

The random number that results from the call to arc4random_uniform() should be <= 30, 30% of the time.