Search code examples
iphonecgpointarc4random

Random CGPoint x value not working


I have 22 images... 11 are (rightwall1, rightwall2, rightwall3, etc) the other 11 are (leftwall1, leftwall2, leftwall3, etc)

I am placing each one ontop of the other by setting their y value to the previous walls y value plus the height of the wall (all walls are the same height).

This works fine!

Now, I was trying to set the x value using arc4random so they would jump all over the place in a certain range ( For the left walls: (-35 to 15) & For the right walls: (330 to 405) )...

The right walls work perfectly, but the left walls, some of them work but most of them don't show up on the screen.

I manually set the x value of one to -45 and it showed up on the screen and that is lower than the arc4random allows it to go.

The only problem I can think of is i'm subtracting wrong for the left walls?

Here is the code to set the walls locations, I have no other code in the whole project yet.

-(void)awakeFromNib {

        rightWall1.center = CGPointMake( ((arc4random()%75)+330), (460-((rightWall1.frame.size.height)/2)) );//460 = bottom of screen
        rightWall2.center = CGPointMake( ((arc4random()%75)+330), ((rightWall1.center.y)-(rightWall2.frame.size.height)) );
        rightWall3.center = CGPointMake( ((arc4random()%75)+330), ((rightWall2.center.y)-(rightWall3.frame.size.height)) );
        rightWall4.center = CGPointMake( ((arc4random()%75)+330), ((rightWall3.center.y)-(rightWall4.frame.size.height)) );
        rightWall5.center = CGPointMake( ((arc4random()%75)+330), ((rightWall4.center.y)-(rightWall5.frame.size.height)) );
        rightWall6.center = CGPointMake( ((arc4random()%75)+330), ((rightWall5.center.y)-(rightWall6.frame.size.height)) );
        rightWall7.center = CGPointMake( ((arc4random()%75)+330), ((rightWall6.center.y)-(rightWall7.frame.size.height)) );
        rightWall8.center = CGPointMake( ((arc4random()%75)+330), ((rightWall7.center.y)-(rightWall8.frame.size.height)) );
        rightWall9.center = CGPointMake( ((arc4random()%75)+330), ((rightWall8.center.y)-(rightWall9.frame.size.height)) );
        rightWall10.center = CGPointMake( ((arc4random()%75)+330), ((rightWall9.center.y)-(rightWall10.frame.size.height)) );
        rightWall11.center = CGPointMake( ((arc4random()%75)+330), ((rightWall10.center.y)-(rightWall11.frame.size.height)) );


        leftWall1.center = CGPointMake( (15-(arc4random()%50)), (460-((leftWall1.frame.size.height)/2)) );
        leftWall2.center = CGPointMake( (15-(arc4random()%50)), ((leftWall1.center.y)-(leftWall2.frame.size.height)) );
        leftWall3.center = CGPointMake( (15-(arc4random()%50)), ((leftWall2.center.y)-(leftWall3.frame.size.height)) );
        leftWall4.center = CGPointMake( (15-(arc4random()%50)), ((leftWall3.center.y)-(leftWall4.frame.size.height)) );
        leftWall5.center = CGPointMake( (15-(arc4random()%50)), ((leftWall4.center.y)-(leftWall5.frame.size.height)) );
        leftWall6.center = CGPointMake( (15-(arc4random()%50)), ((leftWall5.center.y)-(leftWall6.frame.size.height)) );
        leftWall7.center = CGPointMake( (15-(arc4random()%50)), ((leftWall6.center.y)-(leftWall7.frame.size.height)) );
        leftWall8.center = CGPointMake( (15-(arc4random()%50)), ((leftWall7.center.y)-(leftWall8.frame.size.height)) );
        leftWall9.center = CGPointMake( (15-(arc4random()%50)), ((leftWall8.center.y)-(leftWall9.frame.size.height)) );
        leftWall10.center = CGPointMake( (15-(arc4random()%50)), ((leftWall9.center.y)-(leftWall10.frame.size.height)) );
        leftWall11.center = CGPointMake( (15-(arc4random()%50)), ((leftWall10.center.y)-(leftWall11.frame.size.height)) );

}

Solution

  • Turns out you can't get a negative integer value using arc4random (Makes sense because arc4random uses modulus.... integer... ?? haha) So I use a float...

    can't say:

    (-1)*(arc4random() ....
    

    You have to say:

    float num1;
    num1 = -1;
    (num1)*(arc4random() ....
    

    Weird... Same goes for subtracting... you have to add a negative 1 float times the arc4random ..