Question

I’ve made a program that generates an image at a random x-coordinate at the top of the screen. The image then falls down to the bottom. However, I want to keep generating new images (of the same image) every few seconds so that it’s as though these duplicates of the same image are continually “raining” from the top. (Note: Eventually, as I continue to develop this app, I will need to recall the location of each image at any moment, so I believe I will need each spawned image to be part of an array. I also believe I must move each image step-by-step, so I cannot rely on animation).

The problem is: How can I make all of this code repeat every 0.5 seconds so that each newly spawned image has its own moveObject timer. It will be like raindrops falling from the top.

@implementation ViewController {

    UIImageView *_myImage;

}

- (void)viewDidLoad
{
    srand(time(NULL));e
    int random_x_coordinate = rand() % 286;
    CGRect myImageRect = CGRectMake(random_x_coordinate, 0.0f, 40.0f, 40.0f);
    UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect];
    [myImage setImage:[UIImage imageNamed:@"flake.png"]];
    myImage.opaque = YES;
    [self.view addSubview:myImage];
    _myImage = myImage;


    //FALLING BIRDS TIMER
    moveObjectTimer = [NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(moveObject) userInfo:nil repeats:YES];


}
    //FALLING BIRDS MOVER
-(void) moveObject {        // + means down and the number next to it is how many pixels y moves down per each tick of the TIMER above
        _myImage.center = CGPointMake(_myImage.center.x, _myImage.center.y +1);
    }

Answer 1

You have different solutions:

• Just 1 timer in which you update an array of UIImageView (I prefer this one)
• Subclass Imageview and put the timer inside the class so each one would have its own timer
• Maybe you can use [UIView animateWithDuration... instead of timers, but not sure if you can use many at the same time.