At this point we have a world, we have edges to hold everything in, and we have a ball. Now we need to get it all moving. As you might expect, we handle this in the update method.
-(void)update:(ccTime)dt {
// Step the world forward
world->Step(dt, 10, 10);
// Iterate through all bodies in the world
for(b2Body *b = world->GetBodyList(); b;b=b->GetNext()) {
if (b->GetUserData() != NULL) {
// Get the sprite for this body
PhysicsSprite *sprite =
(PhysicsSprite*)b->GetUserData();
// Speed clamp for balls
if (sprite.tag == kBall) {
static int maxSpeed = 15;
b2Vec2 velocity = b->GetLinearVelocity();
float32 speed = velocity.Length();
if (speed > maxSpeed) {
b->SetLinearDamping(0.5);
} else if (speed < maxSpeed) {
b->SetLinearDamping(0.0);
}
...