How to get multiple sprites to bounce off the bounds of a scene in Objective-C - objective-c

Question

I have a game I'm creating with sprite-kit with 25 sprites that are all children of one sprite node BOMNeutNode. At the beginning of the game I create 25 child nodes within the scene using a for-loop, and set them all moving in a random direction using physicsBody.velocity.
What I want to do is to get them to bounce off the bounds of the scene when they reach the edge. I assumed the code below would do the trick to begin with, but it only seems to work on 1 of the 25 nodes (for that one node it is working perfectly well). I'm thinking this must be due to where I have this code positioned in my GamePlayScene code. I thought it would be appropriate to put it in the update section of the game run loop. Maybe I have to set this rule in the node itself?
I also thought it might be that I need to identify ALL nodes named #"Neut" but I can't find the syntax to do this. Please let me know if you need more code than I have provided.
(void) update:(NSTimeInterval)currentTime {
BOMNeutNode *neut = (BOMNeutNode*)[self childNodeWithName:#"Neut"];
if (neut.position.y > self.frame.size.height-50) {
neut.physicsBody.velocity = CGVectorMake(0, -100);
} else if (neut.position.y < 50) {
neut.physicsBody.velocity = CGVectorMake(0, 100);
} else if (neut.position.x > self.frame.size.height-50) {
neut.physicsBody.velocity = CGVectorMake(-100, 0);
} else if (neut.position.x < 50) {
neut.physicsBody.velocity = CGVectorMake(100, 0);
}
}
Any suggestions would be greatly appreciated.

Answer 1

One easy way to do this is to add a SKPhysicsBody created with bodyWithEdgeLoopFromRect: to your SKScene. That way the physics engine can handle all the bouncing for you (with the correct angles and everything).
Typically you'd want to add it in your SKScene's didMoveToView: method. Something like:
- (void)didMoveToView:(SKView*)view {
// ... any other setup you might need ...
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(50, 50, self.size.width - 100, self.size.hight - 100)];
}
If you go this route, that should take care of everything; you shouldn't need the code you currently have in your update: method.

Answer 2

The problem is that you have many nodes called Neut and its finding one of them and checking if its inside the frame, what you need to do is to find all nodes with that name and run the code on all of them
-(void)update:(NSTimeInterval)currentTime {
[self enumerateChildNodesWithName:#"Neut" usingBlock:^(SKNode *node, BOOL *stop) {
if (node.position.y > self.frame.size.height-50) {
node.physicsBody.velocity = CGVectorMake(0, -100);
} else if (node.position.y < 50) {
node.physicsBody.velocity = CGVectorMake(0, 100);
} else if (node.position.x > self.frame.size.height-50) {
node.physicsBody.velocity = CGVectorMake(-100, 0);
} else if (node.position.x < 50) {
node.physicsBody.velocity = CGVectorMake(100, 0);
}
}];
}