Question

I need some help (duh). I want to generate a random Y position for my game in cocos2d.

So the situation goes like this:
The game spawns a platform every 0.2 second. The iPhone / iPad is in landscape mode. Platform appear on the right of the screen (bigger x than width so that the platform appears outside the screen) and starts moving towards the left end of the screen using CCMoveTo.
I pick a random Y for every platform. The problem is that I do not want to spawn a platform on top of another. This means that I need to make a randY which is not “already taken”.
The code I’ve tried so far is this:

//this is a part of code from my addPlatform function. This part in particular cares for the generation of my Y coordinate.
int randY = arc4random() % (int)(3 * (winSize.height/4)); //This prevents to spawn a Y larger than 3/4 of the screen

//here I would like to loop long enough to find a good Y
while (![self isGoodPlatformY:randY])
{
    randY = arc4random() % (int)(3 * (winSize.height/4));
}

The next part is my isGoodPlatformY function

- (bool)isGoodPlatformY:(int)platY
{
    CGSize winSize = [[CCDirector sharedDirector] winSize];
    int padding = 100;
    bool ok = true;
    for (CCSprite *body in [self children])
    {
        if (body.tag > platformBody)
        {
            if (body.position.x < (winSize.width - padding))
            {
                if (abs(body.position.y - platY) < 20)
                {
                    ok = false;
                }
            }
        }
    }
return ok;
}

I loop through all the bodies with larger tag than my platform. I have different types of platform which I separate by using tag. If the body is a platform I first check the X coordinate. If the platform is enough away (padding) I can spawn a new one at that exact point so I check the next one. If not I want to check the Y of that platform. If the Y coordinate is less than 20 pixels in this case I must find a new Y so thats why set the bool to false and return it after the for loop.
I know there is no need for those curly brackets but I was testing some other stuff, thats why I put them there.

This doesn’t seem to work. Hope I made myself clear what I want to accomplish. Any help from your side would be much appreciated. Hope I didn’t miss something too newbie style 🙂

I tagged the question in other languages to because this problem could occur “everywhere”.

Answer 1

Now I have discovered that I can answer my own questions 🙂 (silly me). So yeah, the problem was fixed a long time ago but to anyone who might be reading this, the solution was to change the line:

if (body.position.x < (winSize.width - padding))

To:

if (body.position.x > (winSize.width - padding))