sprite kit removing specific nodes - ios

Question

I am trying to create a game where a character runs forever to the right (the game is landscape). On the ground there are spikes that the character can jump over. Currently, I am creating a new (and somewhat random) set of spikes in almost a checkpoint-like style where once the character reaches a certain distance, the next set of randomly organized spikes are created and the checkpoint distance gets pushed back and so on. Along with the spikes, I have a separate but very similar checkpoint-like system that is used to create the tiles that make up the ground.
This is my code for that portion, 'endlessX' and 'endlessGroundX' are the checkpoint value:
- (void) didSimulatePhysics {
if (player.position.x > endlessX) {
int random = player.position.x + self.frame.size.width;
[self createSpike:random];
endlessX += self.frame.size.width/2.2 + arc4random_uniform(30);
}
if (player.position.x + self.frame.size.width > endlessGroundX) {
[self createGround:endlessGroundX];
endlessGroundX += tile1.frame.size.width;
}
[self centerOnNode: player];
}
The parameter of the createSpike and createGround method is just the 'x' value for the SKSpriteNodes.
I am currently having it as the character itself is the one moving and the spikes and tiles are stationary. This is how I am creating the character:
-(void) createPlayer {
player = [SKSpriteNode spriteNodeWithImageNamed:#"base"];
player.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
player.name = #"player";
player.zPosition = 60;
player.xScale = 0.8;
player.yScale = 0.8;
player.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:player.frame.size.height/2];
player.physicsBody.mass = 1;
player.physicsBody.linearDamping = 0.0;
player.physicsBody.angularDamping = 0.0;
player.physicsBody.friction = 0.0;
player.physicsBody.restitution = 0.0;
player.physicsBody.allowsRotation = NO;
player.physicsBody.dynamic = YES;
player.physicsBody.velocity = CGVectorMake(400, 0);
player.physicsBody.categoryBitMask = playerCategory;
player.physicsBody.collisionBitMask = wallCategory;
player.physicsBody.contactTestBitMask = wallCategory | spikeCategory;
[myWorld addChild:player];
}
With that, the character will never lose any of its kinetic energy to friction or any other force like that. Then, I am using the 'center on node' method that apple used in their adventure game so that the character will always remain in the same x-position on the screen:
- (void) centerOnNode: (SKSpriteNode *) node {
CGPoint cameraPositionInScene = [node.scene convertPoint:node.position fromNode:node.parent];
node.parent.position = CGPointMake(self.frame.size.width/5 + node.parent.position.x - cameraPositionInScene.x, node.parent.position.y);
}
I am calling this method in 'didSimulatePhysics.'
When I run this for some time, the programs gets slower and slower. I am guessing that that is due to the fact that I am never removing these nodes and they are always being added. However, to fix this problem, I tried doing something like this:
-(void)update:(CFTimeInterval)currentTime {
[self enumerateChildNodesWithName:#"*" usingBlock:^(SKNode *node, BOOL *stop) {
if (node.position.x + 50 < player.position.x) {
[node removeFromParent];
}
}];
}
(the +50 would be just to make sure that the node is off the screen before removing it)
However, when I did this, instead of removing the specific node that satisfies the 'if' statement, the program removes all of the sprite nodes. Is there a different method or something that I am missing to fix this? Or are there any other simple ways to remove the specific nodes?

Answer 1

Lacking quite a few details, like how you are animating the spikes for instance, makes it a bit hard to be too specific. Nevertheless, from what you are sharing I guess you might be looking for something a little like this:
SKAction *moveSpikeAction = [SKAction moveToX:-50 duration:5];
SKAction *removeSpikeAction = [SKAction removeFromParent];
SKAction *spikeSequence = [SKAction sequence:#[moveSpikeAction, removeSpikeAction]];
[yourSpikeSpriteNode runAction:spikeSequence];
The idea simply being that when the spike has animated to the off screen position you use the removeFromParent action to clear it.