I'm trying to create a game, where the objects need to chase food. Right now the objects speeds up, when the food is within the given radius. But I need the speed to always be the same.
Any suggestions how to fix this? I have tried to add an SKAction under the chase function, where I set the position.x and position.y, but I can't make it work correct.
Fish class:
class Fish:SKSpriteNode{
private let kMovingAroundKey = "movingAround"
private let kFishSpeed:CGFloat = 4.5
private var swimmingSpeed:CGFloat = 100.0
private let sensorRadius:CGFloat = 100.0
private weak var food:SKSpriteNode! = nil //the food node that this fish currently chase
override init(texture: SKTexture?, color: UIColor, size: CGSize) {
super.init(texture: texture, color: color, size: size)
physicsBody = SKPhysicsBody(rectangleOf: size)
physicsBody?.affectedByGravity = false
physicsBody?.categoryBitMask = Collider.fish
physicsBody?.contactTestBitMask = Collider.food
physicsBody?.collisionBitMask = 0x0 //No collisions with fish, only contact detection
name = "fish"
let sensor = SKShapeNode(circleOfRadius: 100)
sensor.fillColor = .red
sensor.zPosition = -1
sensor.alpha = 0.1
addChild(sensor)
}
func getDistanceFromFood()->CGFloat? {
if let food = self.food {
return self.position.distance(point: food.position)
}
return nil
}
func lock(food:SKSpriteNode){
//We are chasing a food node at the moment
if let currentDistanceFromFood = self.getDistanceFromFood() {
if (currentDistanceFromFood > self.position.distance(point: food.position)){
//chase the closer food node
self.food = food
self.stopMovingAround()
}//else, continue chasing the last locked food node
//We are not chasing the food node at the moment
}else{
//go and chase then
if food.position.distance(point: self.position) <= self.sensorRadius {
self.food = food
self.stopMovingAround()
}
}
}
//Helper method. Not used currently. You can use this method to prevent chasing another (say closer) food while already chasing one
func isChasing(food:SKSpriteNode)->Bool{
if self.food != nil {
if self.food == food {
return true
}
}
return false
}
func stopMovingAround(){
if self.action(forKey: kMovingAroundKey) != nil{
removeAction(forKey: kMovingAroundKey)
}
}
//MARK: Chasing the food
//This method is called many times in a second
func chase(within rect:CGRect){
guard let food = self.food else {
if action(forKey: kMovingAroundKey) == nil {
self.moveAround(within: rect)
}
return
}
//Check if food is in the water
if rect.contains(food.frame.origin) {
//Take a detailed look in my Stackoverflow answer of how chasing works : https://stackoverflow.com/a/36235426
let dx = food.position.x - self.position.x
let dy = food.position.y - self.position.y
let angle = atan2(dy, dx)
let vx = cos(angle) * kFishSpeed
let vy = sin(angle) * kFishSpeed
position.x += vx
position.y += vy
}
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func moveAround(within rect:CGRect){
if scene != nil {
//Go randomly around the screen within view bounds
let point = rect.randomPoint()
//Formula: time = distance / speed
let duration = TimeInterval(point.distance(point: position) / self.swimmingSpeed)
let move = SKAction.move(to: point, duration: duration)
let block = SKAction.run {
[unowned self] in
self.moveAround(within: rect)
}
let loop = SKAction.sequence([move,block])
run(loop, withKey: kMovingAroundKey)
}
}
}
Gamescene where you can see the update function.
override func update(_ currentTime: TimeInterval) {
self.enumerateChildNodes(withName: "fish") {
[unowned self] node, stop in
if let fish = node as? Fish {
self.enumerateChildNodes(withName: "food") {
node, stop in
fish.lock(food: node as! SKSpriteNode)
}
fish.chase(within: self.water.frame)
}
}
}
