How to delete bodies which have gone off screen?

[mh@pixar.com]

What's the right way to delete a body?

In Demos/Plink.c, I changed this code:

Code: Select all

// Iterate over all of the bodies and reset the ones that have fallen offscreen.
static void
eachBody(cpBody *body, void *unused)
{
        if(body->p.y < -260 || fabsf(body->p.x) > 340){
                cpFloat x = rand()/(cpFloat)RAND_MAX*640 - 320;
                body->p = cpv(x, 260);
        }
}

to:

Code: Select all

// Delete the bodies which have fallen off-screen
static void
eachBody(cpBody *body, void *unused)
{
        if(body->p.y < -260 ){
                cpBodyFree(body);
        }
}

expecting that this would delete all the bodies as they fell off-screen, but it gives me a segmentation fault.

Is there something else I need to do to delete bodies?

[slembcke]

You need to remove the body from the space before you free it.

[mh@pixar.com]

Sweet, thanks!

For the record, here's how to change the Plink demo so that it's a one-shot dump of pentagons that get cleaned up once they fall off the screen.

1. Add this line to the "//Add lots of pentagons" loop. This is so we can free the shape attached to the body.

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		body->data=shape;

2. remove the shape and body from the space, then free the shape and body. It doesn't seem to matter if you remove/free the shape first or the body first, so long as you keep in mind that you lose the pointer to the shape when you free the body.

ddd

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	if(body->p.y < -260 ){
		cpSpaceRemoveShape(space, body->data);
		cpSpaceRemoveBody(space, body);
		cpShapeFree(body->data);
		cpBodyFree(body);
	}

[Rb_]

Any idea how this works with iphone development using an NSTimer?

Currently I have my main 'setupChipmunk' method creating the body & shapes, then at the bottom it starts the NSTimer which within its method allows me to check and see when its fallen off the bottom of the screen :

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- (void)tick:(NSTimer *)timer { 
   
 // Tell Chipmunk to take another "step" in the simulation  
   
 cpSpaceStep(space, 1.0f/60.0f);  
	 
	 if(ball.center.y > self.view.bounds.size.height) {
		 score_int++;
		 score.text = [NSString stringWithFormat:@"%d",score_int];
		 
		 	ballBody->data=shape
		 cpSpaceRemoveShape(space, ballBody->data);
		 cpSpaceRemoveBody(space, ballBody);
		cpShapeFree(ballBody->data);
		 cpBodyFree(ballBody);

Using the above it currently fires back a ballBody undeclared method. I'm new to iphone development so its probably something ridiculously obvious, I understand that the reason it's undeclared is down to this method being another private segment of the application, but I am wholly unsure on how to make ballBody global so I can access it.

Any help would be massively appreciated.

Thanks in advance