How do I make my character move sideways? Xcode 6 Sprite Kit - ios

Question

I am making a simple side scrolling game using apple's swift programming language and I want to make my character move left when the left half of the screen is touched and right when the other half is touched. I have done this using this code:
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
if location.x < CGRectGetMidX(self.frame){
character.position.x -= 30
} else if location.x > CGRectGetMidX(self.frame){
character.position.x += 30
} else {
println("jump")
}
}
but he stops moving immediately after he moves 30 px over. my question is, can someone explain how to make him keep moving until the user lifts their finger?
This is my GameScene.swift file:
import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
let character = SKSpriteNode(texture: SKTexture(imageNamed: "character"))
override func didMoveToView(view: SKView) {
/* Setup your scene here */
//world
self.physicsWorld.gravity = CGVectorMake(0.0, -5.0)
//background
var background = SKSpriteNode(imageNamed: "background")
background.size.height = self.frame.size.height
background.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame))
self.addChild(background)
//character
character.position = CGPointMake(self.frame.size.width * 0.6, self.frame.size.height * 0.6)
character.setScale(0.015)
character.physicsBody = SKPhysicsBody(circleOfRadius: CGFloat(character.size.width / 2))
var charPos = character.position
character.physicsBody?.dynamic = true
self.addChild(character)
//platform 1
var platformTexture = SKTexture(imageNamed: "platform")
var platform = SKSpriteNode(texture: platformTexture)
platform.position = CGPointMake(self.frame.size.width * 0.6, CGRectGetMidY(self.frame))
platform.physicsBody = SKPhysicsBody(rectangleOfSize: platform.size)
platform.physicsBody?.dynamic = false
platform.setScale(0.25)
self.addChild(platform)
//platform 2
var platformTexture2 = SKTexture(imageNamed: "platform")
var platform2 = SKSpriteNode(texture: platformTexture2)
platform2.position = CGPointMake(self.frame.size.width * 0.4, self.frame.size.height * 0.3)
platform2.physicsBody = SKPhysicsBody(rectangleOfSize: platform2.size)
platform2.physicsBody?.dynamic = false
platform2.setScale(0.25)
self.addChild(platform2)
//platform main
var platformTexture3 = SKTexture(imageNamed: "platform")
var platform3 = SKSpriteNode(texture: platformTexture2)
platform3.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMinY(self.frame) + platform3.size.height / 3)
platform3.physicsBody = SKPhysicsBody(rectangleOfSize: platform3.size)
platform3.physicsBody?.dynamic = false
platform3.setScale(1)
platform3.size.width = platform3.size.width * CGFloat(2.0)
self.addChild(platform3)
}
override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
/* Called when a touch begins */
func update(currentTime: CFTimeInterval) {
/* Called before each frame is rendered */
}
}
}

Answer 1

You have to apply force constantly to character in every update: call in order to move it without stopping. You can also apply impulses in order to move character, or make it jump. Here is an example based on you code, to give you a basic idea how you can move characters using physics (or by changing velocity vector of a character manually). Look through the comments to find what is important.
import SpriteKit
class GameScene: SKScene, SKPhysicsContactDelegate {
let character = SKSpriteNode(texture: SKTexture(imageNamed: "pauseButton"))
//Boolean variable to store information about move signal (updated in touchesBegan and touchesEnded method)
var move = false
override func didMoveToView(view: SKView) {
/* Setup your scene here */
//world
self.physicsWorld.gravity = CGVectorMake(0.0, -5.0)
self.physicsWorld.contactDelegate = self; //don't forget to set contact delegate if you want to use contact detection and methods like didBeginContact and didEndContact
//background
//just a physical border so that character can't escape from us :)
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
//character
character.position = CGPointMake(self.frame.size.width * 0.6, self.frame.size.height * 0.6)
character.setScale(0.415)
character.physicsBody = SKPhysicsBody(circleOfRadius: CGFloat(character.size.width / 2))
var charPos = character.position
character.physicsBody?.dynamic = true
self.addChild(character)
}
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
/* Called when a touch begins */
for touch: AnyObject in touches {
let location = touch.locationInNode(self)
//Hold finger at upper area to move character constantly to the right.
if location.y > 400{
//moving allowed, force is applied in update method. read the docs about applyImpulse and applyForce methods and the differences between those two.
move = true
}else{
if location.x < CGRectGetMidX(self.frame){
character.physicsBody?.applyImpulse(CGVector(dx: -30, dy: 0))
//tap somewhere above this to make character jump
if(location.y > 250) {
character.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 50))
}
} else if location.x > CGRectGetMidX(self.frame){
character.physicsBody?.applyImpulse(CGVector(dx: 30, dy: 0))
//tap somewhere above this to make character jump
if(location.y > 250) {
character.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 50))
}
}
}
}
}
override func touchesEnded(touches: NSSet, withEvent event: UIEvent) {
move = false
//character.physicsBody?.velocity = CGVector(dx: 0, dy: 0) //you can make character to stop by manually setting its velocity vector to (0,0)
}
override func update(currentTime: CFTimeInterval) {
if(move){character.physicsBody?.applyForce(CGVector(dx: 30, dy: 0))}
//if(move){character.position = CGPoint(x: character.position.x+1, y:character.position.y)} //not recommended if you need physics simulation (eg. collisions)
}
}
Note that you can change node's position in every update call to achieve what you want, like this :
if(move){character.position = CGPoint(x: character.position.x+1, y:character.position.y)}
But this way you will pull the node out of physics simulation and you can experience unexpected results. Search SO about this topic, there are some good posts about all this.
Hope this helps a bit.