Sprites following each other - swift

Question

Thanks in advance. I currently have a sprite controlled by the tilting of the device and would like every so often(NSTimer) for another sprite to appear behind it following it with the same physics. I have it set up, but i need the position to update every second so it follow behind it. How would I go about this? This is what I've tried/done.
let snakeBodyY = snakeHead.position.y - 5
let snakeBodyX = snakeHead.position.x - 5
snakeHead = SKSpriteNode(imageNamed: "snakeHead")
snakeHead.size = CGSize(width: 60, height: 60)
snakeHead.position = CGPoint(x: self.frame.midX, y: self.frame.midY - 50)
self.addChild(snakeHead)
snakeBody = SKSpriteNode(imageNamed: "snakeBody")
snakeBody.size = CGSize(width: 50, height: 50)
snakeBody.position.x = snakeBodyX
snakeBody.position.y = snakeBodyY
self.addChild(snakeBody)

Answer 1

Depends on how advance you need it,
if this is a free range 2D world you could assign the each new body to the tail so that the positions are relative to the snake, and always try to make the body parts move to the center of the previous body part up to the head.
Set up your sprite like this:
let snake = SKNode...
let head = SKSpriteNode...
let tail = SKSpriteNode...
//make sure you set up your positions for each body part, they should be relative to snake, not the screen
//setup collision so that tail and head can collide
head.physicsBody = SKPhysicsBody...
head.categoryBitMask = 1
head.collisionBitMask = 1
tail.physicsBody = SKPhysicsBody...
tail.categoryBitMask = 1
tail.collisionBitMask = 1
//setup restitution so that they do not bounce when colliding
head.restitution = 0
tail.restitution = 0
//add the parts to snake
snake.addChild(head)
snake.addChild(tail)
//Now you have a snake with a head and tail create an action to move the snake tail to the center of head
let moveToCenter = SKAction.moveTo(head.position, duration:0)
tail.runAction(moveToCenter)
//this will move the talk to try to get to the center of head, but collision physics will stop it from overlapping.
//Now everytime you want to add a new body
let body = SKSpriteNode...
body.physicsBody = SKPhysicsBody...
body.categoryBitMask = 1
body.collisionBitMask = 1
body.restitution = 0
snake.addChild(body)
let moveToCenter = SKAction.moveTo(tail.position, duration:0)
body.runAction(moveToCenter)
tail = body //lets make the tail the new piece to add
//Then on every update loop. you want to go through the children and do something like this
let previousChild = head
for child in snake.children
{
if child == head
{
continue;
}
child.removeAllActions()
let moveToCenter = SKAction.moveTo(previousChild.position, duration:0)
child.runAction(moveToCenter)
previousChild = child
}
Now if you find that this code may end up running slow for you, and don't mind a more stiff approach, you could also look up SKAction.followPath. Now I am not going to get into the details here, but basically what you need to do is record how your snake moves, then you generate a path with it, and use SKAction.followPath to make all the body parts move along the path.
If you are working in a 2d tiled world that only allows vertical and horizontal movement, you create an array of your sprites, and every time your snake makes a movement, you go down the snake and change its position to the previous body parts position