Moving a ball randomly

[Momeks]

Hi , I am trying to move a ball across the screen with random coordinates . but my object moves just around x axis ! here is my code :

PHP Code:

 [UIView beginAnimations:nil context:nil];
 [UIView setAnimationDuration:0.70];
 [UIView setAnimationRepeatCount:1000];
 [UIView setAnimationRepeatAutoreverses:YES];

 CGFloat x = (CGFloat) random()/(CGFloat) RAND_MAX * self.view.bounds.size.width;
 CGFloat y = (CGFloat) random()/(CGFloat) RAND_MAX * self.view.bounds.size.height;


 CGPoint squarePostion = CGPointMake(y, x);
 blue3.center = squarePostion;

 [UIView commitAnimations]; 


Thank you .

[Duncan C]

Originally Posted by Momeks

Hi , I am trying to move a ball across the screen with random coordinates . but my object moves just around x axis ! here is my code :

PHP Code:

 [UIView beginAnimations:nil context:nil];
 [UIView setAnimationDuration:0.70];
 [UIView setAnimationRepeatCount:1000];
 [UIView setAnimationRepeatAutoreverses:YES];

 CGFloat x = (CGFloat) random()/(CGFloat) RAND_MAX * self.view.bounds.size.width;
 CGFloat y = (CGFloat) random()/(CGFloat) RAND_MAX * self.view.bounds.size.height;


 CGPoint squarePostion = CGPointMake(y, x);
 blue3.center = squarePostion;

 [UIView commitAnimations]; 


Thank you .

Several things.

You should use arc4random(), not random(). arc4radom gives much better random numbers, and it's self-seeding, so you don't get the same sequence every time you run your program.

Second, you need to use the modulo operator ("%") to get a random number in a given range. Try this:

 CGFloat x = (CGFloat) arc4random() % self.view.bounds.size.width;
 CGFloat y = (CGFloat) random() % self.view.bounds.size.height;

Note that if you let the ball's center move all the way from 0 to the height/width of your bounds, the ball will be 1/2 off screen at the max/min value. You should really keep it from going below ball.bounds.size.width/2, ball.bounds.size.height/2, and don't let it go above self.view.bounds.size.width - ball.bounds.size.width/2, self.view.bounds.size.height - ball.bounds.size.height/2;

[Momeks]

Originally Posted by Duncan C

Several things.

You should use arc4random(), not random(). arc4radom gives much better random numbers, and it's self-seeding, so you don't get the same sequence every time you run your program...........

thank you ,, but the compiler gives me this errors :

[Duncan C]

Originally Posted by Momeks

thank you ,, but the compiler gives me this errors :

Oh, sorry about that. I forgot that CGSize variables are floats. You need to cast them to integers:

 CGFloat x = (CGFloat) arc4random() % (int)self.view.bounds.size.width;
 CGFloat y = (CGFloat) random() % (int) self.view.bounds.size.height;

[Momeks]

Originally Posted by Duncan C

Oh, sorry about that. I forgot that CGSize variables are floats. You need to cast them to integers:

 CGFloat x = (CGFloat) arc4random() % (int)self.view.bounds.size.width;
 CGFloat y = (CGFloat) random() % (int) self.view.bounds.size.height;

Thank you , but did you test your code? because have same errors !

[UIView beginAnimations:nil context:nil];
	[UIView setAnimationDuration:0.70];
	[UIView setAnimationRepeatCount:1000];
	[UIView setAnimationRepeatAutoreverses:YES];
	

	CGFloat x = (CGFloat) arc4random() % (int) self.view.bounds.size.width;
	CGFloat y = (CGFloat) random() % (int) self.view.bounds.size.height;
	
	CGPoint squarePostion = CGPointMake(y, x);
	blue1.center = squarePostion ;

I think problem its because of % ! , when I change % to / or * works fine ! but doesn't move great .

[Duncan C]

Originally Posted by Momeks

Thank you , but did you test your code? because have same errors !

[UIView beginAnimations:nil context:nil];
	[UIView setAnimationDuration:0.70];
	[UIView setAnimationRepeatCount:1000];
	[UIView setAnimationRepeatAutoreverses:YES];
	

	CGFloat x = (CGFloat) arc4random() % (int) self.view.bounds.size.width;
	CGFloat y = (CGFloat) random() % (int) self.view.bounds.size.height;
	
	CGPoint squarePostion = CGPointMake(y, x);
	blue1.center = squarePostion ;

I think problem its because of % ! , when I change % to / or * works fine ! but doesn't move great .

No, it's not my code, it's yours. I'm trying to help you out. You need to experiment and figure this out for yourself. I'm trying to work on my own project and help out a little on the forum too.

You might need an extra pair of parenthesis around the type cast, like this:

CGFloat x = (CGFloat) arc4random() % ((int) self.view.bounds.size.width);
CGFloat y = (CGFloat) random() % ((int) self.view.bounds.size.height);

[Momeks]

finally solved the compiler error ! and it works ! ,but still doesn't move randomly !!!! just specific axis !!!! i don't know why !

	
    CGFloat x = (CGFloat) (arc4random() % (int) self.view.bounds.size.width);
    CGFloat y =  (CGFloat) ( random() % (int)self.view.bounds.size.height );

[Duncan C]

Originally Posted by Momeks

finally solved the compiler error ! and it works ! ,but still doesn't move randomly !!!! just specific axis !!!! i don't know why !

	
    CGFloat x = (CGFloat) (arc4random() % (int) self.view.bounds.size.width);
    CGFloat y =  (CGFloat) ( random() % (int)self.view.bounds.size.height );

I only changed the code that calculated x. You'll need to do the same thing for y.