Sprite Kit - Objective c，同时移动多个 SKNode

Question

i have this method that makes the Lines

    lineaGuida_Img = [SKTexture textureWithImageNamed:@"LineaGuida copia.jpeg"];  
_Linea = [SKNode node];
_Linea.position = CGPointMake((self.frame.size.width / 7 ) * 2, self.frame.size.height / 2 );
_Linea.zPosition = -10;

SKSpriteNode * linea = [SKSpriteNode spriteNodeWithTexture:lineaGuida_Img];
linea.position = CGPointMake(0,0);
linea.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:linea.size];
linea.physicsBody.dynamic = FALSE;
linea.physicsBody.collisionBitMask = 0;
linea.physicsBody.categoryBitMask = CollisionEnemy;
[_Linea addChild:linea];

[self addChild:_Linea];

In the touchesBegan method when i touch the screen, the player is always on the center of screen, and those lines behind him have to move by -x.

  [_Linea runAction:[SKAction moveByX: -(self.size.width/8) y:0 duration:0.1]];
  [self spawn_Lines];

But this action is only executed by the last SKNode. I need to apply this to all Lines simultaneously. After that, when the line's position is less then the player's position, the line must be deleted.

Answer 1

SpriteKit uses a tree based model, so whatever the parent node does, the children fall suit. Create an SKNode to house all of your lines, add all of your lines to this SKNode, then apply the actions to the SKNode, not the lines.

Answer 2

Add them to NSMutableArray to keep the reference and use for each loop to make each one run the action. I would recommend you to use NSTimer to provide [SKAction moveByX: -1 y:0 duration:0]] with constant speed which will result in the same motion as you already used. Each time this NSTimer execute you will check all positions of object from your NSMutableArray and than delete it if it fits your conditions. Be careful when you want to lose the reference completely use [object removeFromParent]; and remove it also from your NSMutableArray to avoid lose of performance later on. For this I use rather forLoop with continue method