Change image name of global variable - swift

I'm creating a Snake Game using swift and the library SpriteKit.

At the top of my program I declare a variable

import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
var player = SKSpriteNode(imageNamed: "head")
[...]
}

In this way I can access to this variable in all of my functions. But I'd like to change the snake's image when the it moves.
For example, if the snake moves Up, I'd like to display the image of the snake looking up.

So I have this code to control the movements of the snake

if movesController[0]==true{
playerY += 56.0000000
}
if movesController[1]==true{
playerY -= 56.0000000
}
if movesController[2]==true{
playerX += 56.0000000
}
if movesController[3]==true{
playerX -= 56.0000000
}

and to change the image of the snake I thought I could just do this

if movesController[0]==true{
playerY += 56.0000000
player = SKSpriteNode(imageNamed: "head_up")
}
if movesController[1]==true{
playerY -= 56.0000000
player = SKSpriteNode(imageNamed: "head_down")
}
if movesController[2]==true{
playerX += 56.0000000
player = SKSpriteNode(imageNamed: "head_right")
}
if movesController[3]==true{
playerX -= 56.0000000
player = SKSpriteNode(imageNamed: "head_left")
}

But adding this 4 lines, the Snake is unable to move...
So I tried changing the declaration of the player variable

import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
var imageName = "head"
var player = SKSpriteNode(imageNamed: "\("imageName)")
[...]
}

and then change the 4 lines I added before with imageName = "move_up" (or down - left - right)

But at the start of the program it gave me an error

Cannot use instance member 'imageName' within property initializer; property initializers run before 'self' is available

What should I do? My last option is to create another playerVariable and put it above the real snake image, but it would mean adding more nodes for nothing.

Actually, your way to solve this problem is true.Put self before the imageName variable. It would be work.

  import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
var imageName = "head"
var player = SKSpriteNode(imageNamed: "\("self.imageName)")
[...]
}

You must change player's texture, but not create new player at each step. Try add this function:

func changeHead(imageNamed name: String){
player.texture = SKTexture(imageNamed: name)
}

And the program text will be changed in this way:

if movesController[0]==true{
playerY += 56.0000000
changeHead(imageNamed: "head_up")
}
if movesController[1]==true{
playerY -= 56.0000000
changeHead(imageNamed: "head_down")
}
if movesController[2]==true{
playerX += 56.0000000
changeHead(imageNamed: "head_right")
}
if movesController[3]==true{
playerX -= 56.0000000
changeHead(imageNamed: "head_left")
}