having a node follow at a constant speed - ios

Question

I'm trying to make a small mini game where you drag a ball around the screen and every 10 seconds a ball gets added in that follows you. so far the you can drag a ball around the screen and a ball follows you, but when another ball gets added in the balls group together. I think this is because the ball is following me depending on how fast I'm going. so is there a certain way in which I can have the balls follow me at a certain speed constantly, like 10 pixels a second or something, and that should prevent the balls from grouping together.
I am currently working on the score so it should soon go up every second you survive. and you die if you touch one of the balls.
below is the code and a short gif of my current code
!(https://gyazo.com/1d6a56527bfd0884e8a26cff730f4e03)
import SpriteKit
import GameplayKit
struct physicsCatagory{
static let me : UInt32 = 0x1 << 1
static let enemy : UInt32 = 0x1 << 2
}
class GameScene: SKScene, SKPhysicsContactDelegate {
private func makeEnemyName() -> String {
enemyCounter += 1
return "enemy\(enemyCounter)"
}
private func addEnemyToDict(enemy: SKSpriteNode, target: SKSpriteNode) {
if let name = enemy.name { spriteDictionary[name] = (enemy, target) }
else { print("enemy not found") }
}
private func removeEnemyFromDict(enemy: SKSpriteNode) {
if let name = enemy.name { spriteDictionary[name] = nil }
else { print("enemy not removed from dictionary!") }
}
private func moveFollowerToTarget(_ sprites: FollowerAndTarget) {
let action = SKAction.move(to: sprites.target.position, duration: 1)
sprites.follower.run(action)
}
private func allEnemiesMoveToTarget() {
for sprites in spriteDictionary.values {
moveFollowerToTarget(sprites)
}
}
let enemySpeed: CGFloat = 300
var me = SKSpriteNode()
// Tuple to keep track of enemy objects:
typealias FollowerAndTarget = (follower: SKSpriteNode, target: SKSpriteNode)
// [followerName: (followerSprite, targetSprite):
var spriteDictionary: [String: FollowerAndTarget] = [:]
// Give each enemy a unique name for the dictionary:
var enemyCounter = 0
var died = Bool()
override func didMove(to view: SKView) {
createScene()
}
func createEnemy () {
if died == true{
}
else {
let enemy = SKSpriteNode(imageNamed: "enemy1")
enemy.name = makeEnemyName()
addEnemyToDict(enemy: enemy, target: me)
moveFollowerToTarget((follower: enemy, target: me))
enemy.size = CGSize(width: 60, height: 60)
enemy.position = CGPoint(x:667, y: 200)
enemy.physicsBody?.restitution = 0.5
enemy.physicsBody = SKPhysicsBody(circleOfRadius: 60)
enemy.physicsBody?.affectedByGravity = false
enemy.zPosition = 2
enemy.physicsBody?.linearDamping = 0
enemy.physicsBody?.isDynamic = true
enemy.physicsBody?.categoryBitMask = physicsCatagory.enemy
enemy.physicsBody?.collisionBitMask = physicsCatagory.me
enemy.physicsBody?.contactTestBitMask = physicsCatagory.me
addChild(enemy)
}
}
func didBegin(_ contact: SKPhysicsContact) {
let firstBody = contact.bodyA
let secondBody = contact.bodyB
if firstBody.categoryBitMask == physicsCatagory.me && secondBody.categoryBitMask == physicsCatagory.enemy || firstBody.categoryBitMask == physicsCatagory.enemy && secondBody.categoryBitMask == physicsCatagory.me {
died = true
restartScene()
}
}
var lose: SKLabelNode!
func restartScene(){
self.removeAllChildren()
self.removeAllActions()
died = false
if let nextScene = GameScene(fileNamed: "menuScene"){
nextScene.scaleMode = self.scaleMode
let transition = SKTransition.fade(withDuration: 1)
view?.presentScene(nextScene, transition: transition)
}
}
func createScene(){
me = self.childNode(withName: "me") as! SKSpriteNode
me.physicsBody = SKPhysicsBody(circleOfRadius: 20)
me.physicsBody?.affectedByGravity = false
me.physicsBody?.categoryBitMask = physicsCatagory.me
me.physicsBody?.collisionBitMask = physicsCatagory.enemy
me.zPosition = 2
self.physicsWorld.contactDelegate = self
let border = SKPhysicsBody (edgeLoopFrom: self.frame)
border.friction = 0
self.physicsBody = border
run(SKAction.repeatForever(SKAction.sequence([SKAction.run(createEnemy), SKAction.wait(forDuration: 4.0)])))
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
allEnemiesMoveToTarget()
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
allEnemiesMoveToTarget()
}
}
override func update(_ currentTime: TimeInterval) {
// Will iterate through dictonary and then call moveFollowerToTarget()
// thus giving each enemy a new movement action to follow.
allEnemiesMoveToTarget()
}
}

Answer 1

Here you go:
import SpriteKit
import GameplayKit
struct physicsCatagory{
static let me : UInt32 = 0x1 << 1
static let enemy : UInt32 = 0x1 << 2
static let coin : UInt32 = 0x1 << 3
}
class GameScene: SKScene, SKPhysicsContactDelegate {
var lose: SKLabelNode!
var me = SKSpriteNode()
// Tuple to keep track of enemy objects:
typealias FollowerAndTarget = (follower: SKSpriteNode, target: SKSpriteNode)
// [followerName: (followerSprite, targetSprite):
var spriteDictionary: [String: FollowerAndTarget] = [:]
// Give each enemy a unique name for the dictionary:
var enemyCounter = 0
let enemySpeed: CGFloat = 3
var died = Bool()
var timer = SKLabelNode()
var timerValue: Int = 0 {
didSet {
timer.text = "\(timerValue)"
}
}
private func makeEnemyName() -> String {
enemyCounter += 1
return "enemy\(enemyCounter)"
}
private func addEnemyToDict(enemy: SKSpriteNode, target: SKSpriteNode) {
if let name = enemy.name { spriteDictionary[name] = (enemy, target) }
else { print("enemy not found") }
}
private func removeEnemyFromDict(enemy: SKSpriteNode) {
if let name = enemy.name { spriteDictionary[name] = nil }
else { print("enemy not removed from dictionary!") }
}
// dont change anything outside of this, this is what makes the enemy follow you, so i have to have the enemy follow me at a constant speed
private func moveFollowerToTarget(_ sprites: FollowerAndTarget) {
let location = me.position
// Aim
let dx = location.x - sprites.follower.position.x
let dy = location.y - sprites.follower.position.y
let angle = atan2(dy, dx)
sprites.follower.zRotation = angle
// Seek
let vx = cos(angle) * enemySpeed
let vy = sin(angle) * enemySpeed
sprites.follower.position.x += vx
sprites.follower.position.y += vy
}
private func allEnemiesMoveToTarget() {
for sprites in spriteDictionary.values {
moveFollowerToTarget(sprites)
}
}
private func keepEnemiesSeparated() {
for sprites in spriteDictionary.values {
let iterator = sprites.follower
iterator.constraints = []
// get every other follower:
var otherFollowers: [SKSpriteNode] = []
for sprites in spriteDictionary.values {
if sprites.follower == iterator { continue }
else { otherFollowers.append(sprites.follower) }
}
// Assign constrain
for follower in otherFollowers {
let distanceBetween = CGFloat(60)
let constraint = SKConstraint.distance(SKRange(lowerLimit: distanceBetween), to: follower)
iterator.constraints!.append(constraint)
}
}
}
func createEnemy () {
if died { return }
let enemy = SKSpriteNode(color: .green, size: CGSize(width: 60, height: 60))
enemy.size = CGSize(width: 60, height: 60)
enemy.zPosition = 2
enemy.position.y -= size.height / 2
enemy.physicsBody = {
let pb = SKPhysicsBody(circleOfRadius: 30)
pb.restitution = 0.5
pb.affectedByGravity = false
pb.linearDamping = 0
pb.isDynamic = true
pb.categoryBitMask = physicsCatagory.enemy
pb.collisionBitMask = physicsCatagory.me
pb.contactTestBitMask = physicsCatagory.me
return pb
}()
enemy.name = makeEnemyName()
addEnemyToDict(enemy: enemy, target: me)
moveFollowerToTarget((follower: enemy, target: me))
keepEnemiesSeparated()
addChild(enemy)
}
func createCoin () {
let coin = SKSpriteNode(color: .yellow, size: CGSize(width: 20, height: 20))
let height = self.view!.frame.height
let width = self.view!.frame.width
let randomPosition = CGPoint( x:CGFloat( arc4random_uniform( UInt32( floor( width ) ) ) ),
y:CGFloat( arc4random_uniform( UInt32( floor( height ) ) ) )
)
coin.position = randomPosition
addChild(coin)
}
func restartScene(){
self.removeAllChildren()
self.removeAllActions()
died = false
let nextScene = GameScene(size: self.size)
nextScene.scaleMode = self.scaleMode
let transition = SKTransition.fade(withDuration: 1)
view?.presentScene(nextScene, transition: transition)
}
func createScene(){
me = SKSpriteNode(color: .blue, size: CGSize(width: 60, height: 60))
me.physicsBody = SKPhysicsBody(circleOfRadius: 30)
me.physicsBody?.affectedByGravity = false
me.physicsBody?.categoryBitMask = physicsCatagory.me
me.physicsBody?.collisionBitMask = physicsCatagory.enemy
me.zPosition = 2
timer = SKLabelNode(fontNamed: "Chalkduster")
timer.text = "\(timerValue)"
addChild(me)
addChild(timer)
let wait = SKAction.wait(forDuration: 1)
let block = SKAction.run({
[unowned self] in
if self.timerValue >= 0{
self.timerValue += 1
}else{
self.removeAction(forKey: "countdown")
}
})
let sequence = SKAction.sequence([wait,block])
run(SKAction.repeatForever(sequence), withKey: "countdown")
self.physicsWorld.contactDelegate = self
let border = SKPhysicsBody (edgeLoopFrom: self.frame)
border.friction = 0
self.physicsBody = border
run(SKAction.repeatForever(SKAction.sequence([SKAction.run(createEnemy), SKAction.wait(forDuration: 2.0)])))
run(SKAction.repeatForever(SKAction.sequence([SKAction.run(createCoin), SKAction.wait(forDuration: TimeInterval(arc4random_uniform(11) + 5))])))
}
override func didMove(to view: SKView) {
scene?.anchorPoint = CGPoint(x: 0.5, y: 0.5)
createScene()
}
func didBegin(_ contact: SKPhysicsContact) {
let firstBody = contact.bodyA
let secondBody = contact.bodyB
if firstBody.categoryBitMask == physicsCatagory.me && secondBody.categoryBitMask == physicsCatagory.enemy
|| firstBody.categoryBitMask == physicsCatagory.enemy && secondBody.categoryBitMask == physicsCatagory.me {
died = true
restartScene()
}
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
allEnemiesMoveToTarget()
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches{
let location = touch.location(in: self)
me.run(SKAction.moveTo(x: location.x, duration: 0))
me.run(SKAction.moveTo(y: location.y, duration: 0))
allEnemiesMoveToTarget()
}
}
override func update(_ currentTime: TimeInterval) {
// Will iterate through dictonary and then call moveFollowerToTarget()
// thus giving each enemy a new movement action to follow.
allEnemiesMoveToTarget()
}
}