Generate random falling images (xcode)

Question

I'd like to create random images falling from the top of the screen, down to the bottom where they disappear. So far, I've been able to make 1 image fall down, at a fixed spawn point (center), but I'm unsure how to generate many more that spawn at random places on the top (somewhat like a snowfall or rainfall effect).

This is what I have so far:

-(void) viewDidLoad {
    moveObjectTimer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(moveObject) userInfo:nil repeats:YES]; }


-(void) moveObject {        // + means down and 5 is SPEED
    bird.center = CGPointMake(bird.center.x, bird.center.y +5); }

Answer 1

Say suppose you have 10 images in an array, then to select any 10 images at random you would do;

int randomIndex rand()/RAND_MAX * 10 + 1;

Then in some method, you could animate it as;

-(void) moveObject{
   int randomIndex = rand()/RAND_MAX * 10 + 1;
   UIImage *image = [self.myImages objectAtIndex:randomIndex];
   UIImageView *imageView = [[UIImageView alloc] initWithImage: image];
  CGRect mainRect = CGRectMake(view.frame.size.width + image.size.width,view.frame.size.height - image.size.height,image.frame.size.width,image.size.height );
    imageView.frame mainRect;
    [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseIn animations:^{
        mainRect.frame.size.origin.x = 0;
        mainRect.frame.origin.y = 0;
        imageView.frame =mainRect;
    } completion:nil];
}

Your NSTimer should trigger this method and then this would select the random image out of your images, here I suppose 10 images that you have in an array. Then this would animate the images from outside the top/right corner to the bottom left corner at the specified time interval as specified with NSTimer.