contact and collision detection in swift - ios

Question

I am working on a game of falling objects and a ball that avoids those objects ,
let ballCatogary:UInt32 = 0x1 << 0
let objectsCatogary:UInt32 = 0x1 << 1
let bottomWallCatogary:UInt32 = 0x1 << 3
1)the ballcatogary is for the ball node that the user controls
2)the objects category is for the right and left walls , and the falling objects that when the user interacts with ,the game stops
3) the bottomcatogary is a sknode that the objects doesn't interact with , but when it passes through it the score value increases
I assigned each node to its categoryBitMask, but now I don't know what to write in the didBeginContact, all i need is help with the did begin collision method, not how to increase the score or end the game, I got that covered.
my code:
//
// PlayScene.swift
// WalkRun
//
// Created by naeim on 7/10/15.
// Copyright (c) 2015 naeim. All rights reserved.
//
import Foundation
import SpriteKit
class PlayScene: SKScene, SKPhysicsContactDelegate{
var ball = SKSpriteNode(imageNamed: "ball")
var wall = SKNode()
var wallRight = SKNode()
var ballSpeed = CGFloat()
let ballCatogary:UInt32 = 0x1 << 0
let objectsCatogary:UInt32 = 0x1 << 1
let bottomWallCatogary:UInt32 = 0x1 << 3
var endOfScreenRight = CGFloat()
var gameOver = 0
var movingObjects = SKNode()
var score = 0
var scoreLabel = SKLabelNode()
var bigWall = SKSpriteNode()
var tallWall = SKSpriteNode()
override func didMoveToView(view: SKView) {
endOfScreenRight = 100
self.physicsWorld.contactDelegate = self
backgroundColor = UIColor(hex: 0x80d9ff)
self.physicsWorld.gravity = CGVectorMake(-9,0)
self.addChild(movingObjects)
//creating the ball
ball.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMinY(self.frame) + self.ball.size.height * 2)
ball.physicsBody = SKPhysicsBody(circleOfRadius: self.ball.size.width / 2)
ball.zPosition = 10
ball.physicsBody?.categoryBitMask = ballCatogary
ball.physicsBody?.collisionBitMask = objectsCatogary
ball.physicsBody?.contactTestBitMask = objectsCatogary
self.addChild(ball)
//creating the wall of the left
wall.position = CGPointMake(CGRectGetMinX(self.frame),CGRectGetMinY(self.frame))
wall.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(2, self.frame.size.height * 2.0))
wall.physicsBody?.dynamic = false
wall.physicsBody?.categoryBitMask = objectsCatogary
self.addChild(wall)
//creating the wall of the right
wallRight.position = CGPointMake(CGRectGetMaxX(self.frame), CGRectGetMinY(self.frame))
wallRight.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(2, self.frame.size.height * 2.0))
wallRight.physicsBody?.dynamic = false
wallRight.physicsBody?.categoryBitMask = objectsCatogary
self.addChild(wallRight)
//creating the label
scoreLabel.fontName = "Helvetica"
scoreLabel.fontSize = 60
scoreLabel.text = "0"
scoreLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame) )
self.addChild(scoreLabel)
//bottom wall
var bottomWall = SKNode()
bottomWall.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMinY(self.frame) + ball.position.y / 1.4)
bottomWall.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(self.frame.size.width , 1))
bottomWall.physicsBody?.dynamic = false
bottomWall.physicsBody?.affectedByGravity = false
bottomWall.physicsBody?.categoryBitMask = bottomWallCatogary
self.addChild(bottomWall)
var timer = NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: Selector("randObject"), userInfo: nil, repeats: true)
}
//function to randomly choose which object
func randObject(){
if gameOver == 0{
var rand = arc4random_uniform(6)+1
switch(rand){
case 1:
leftObject()
case 2:
middleObject()
case 3:
rightObject()
case 4:
LeftAndMiddleObject()
case 5:
rightAndLeftObject()
case 6:
rightAndMiddleObject()
default:
println("error !! non a number other than 0, 1, 2 has been choosen .")
}
}
}
//function that creates a Bigwall
func createBigWall(PositionX:CGFloat , PositionY:CGFloat){
bigWall = SKSpriteNode(imageNamed: "shortwall")
bigWall.position = CGPointMake(PositionX, PositionY)
bigWall.physicsBody = SKPhysicsBody(rectangleOfSize: self.bigWall.size)
bigWall.physicsBody?.dynamic = false
bigWall.physicsBody?.affectedByGravity = false
bigWall.physicsBody?.categoryBitMask = objectsCatogary
bigWall.physicsBody?.collisionBitMask = ballCatogary
bigWall.physicsBody?.contactTestBitMask = ballCatogary
var moveObjects = SKAction.moveByX(0, y: -self.frame.size.height * 2, duration: NSTimeInterval(self.frame.size.height / 100))
var removeObjects = SKAction.removeFromParent()
var moveAndRemoveObjects = SKAction.sequence([moveObjects,removeObjects])
bigWall.runAction(moveAndRemoveObjects)
movingObjects.addChild(bigWall)
}
//function that creates a Tallwall
func createTallWall(PositionX:CGFloat , PositionY:CGFloat ){
tallWall = SKSpriteNode(imageNamed: "tallwall")
tallWall.position = CGPointMake(PositionX, PositionY)
tallWall.physicsBody = SKPhysicsBody(rectangleOfSize: self.tallWall.size)
tallWall.physicsBody?.dynamic = false
tallWall.physicsBody?.affectedByGravity = false
tallWall.physicsBody?.categoryBitMask = objectsCatogary
tallWall.physicsBody?.collisionBitMask = ballCatogary
tallWall.physicsBody?.contactTestBitMask = ballCatogary
var moveObjects = SKAction.moveByX(0, y: -self.frame.size.height * 2, duration: NSTimeInterval(self.frame.size.height / 100))
var removeObjects = SKAction.removeFromParent()
var moveAndRemoveObjects = SKAction.sequence([moveObjects,removeObjects])
tallWall.runAction(moveAndRemoveObjects)
movingObjects.addChild(tallWall)
}
//function to create the left objects
func leftObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMinX(self.frame) + 30, PositionY: CGRectGetMaxY(self.frame))
}
else
{
createTallWall(CGRectGetMinX(self.frame) - 60, PositionY: CGRectGetMaxY(self.frame))
}
}
//function to create the middle objects
func middleObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMidX(self.frame) , PositionY: CGRectGetMaxY(self.frame))
}
else
{
createTallWall(CGRectGetMidX(self.frame), PositionY: CGRectGetMaxY(self.frame))
}
}
//function to create the right objects
func rightObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMaxX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
}
else
{
createTallWall(CGRectGetMaxX(self.frame) - 60, PositionY: CGRectGetMaxY(self.frame))
}
}
//function to create a right and left object
func rightAndLeftObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMaxX(self.frame) - 30 , PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMinX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
else
{
createBigWall(CGRectGetMinX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMaxX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
}
func rightAndMiddleObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMidX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMaxX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
else
{
createBigWall(CGRectGetMaxX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMinX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
}
func LeftAndMiddleObject(){
var rand = arc4random_uniform(2) + 1
if rand == 1
{
createBigWall(CGRectGetMinX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMidX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
else
{
createBigWall(CGRectGetMidX(self.frame) - 30, PositionY: CGRectGetMaxY(self.frame))
createTallWall(CGRectGetMinX(self.frame) + 60, PositionY: CGRectGetMaxY(self.frame))
}
}
func didBeginContact(contact: SKPhysicsContact) {
// 1. Create local variables for two physics bodies
var firstBody: SKPhysicsBody
var secondBody: SKPhysicsBody
// 2. Assign the two physics bodies so that the one with the lower category is always stored in firstBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
// 3. react to the contact between ball and bottom
if firstBody.categoryBitMask == ballCatogary && secondBody.categoryBitMask == objectsCatogary {
gameOver = 1
movingObjects.speed = 0
}
else
{
println("score ++")
}
}
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
if gameOver == 0 {
ball.physicsBody?.velocity = CGVectorMake(0, 0)
ball.physicsBody?.applyImpulse(CGVectorMake(70,0))
}
}
override func update(currentTime: NSTimeInterval) {
if gameOver == 0 {
}
}
}

Answer 1

I am not sure what are you asking but check this example code:
//This delegate function will call when two body collide with each other
func didBeginContact(contact: SKPhysicsContact) {
// 1. Create local variables for two physics bodies
var firstBody: SKPhysicsBody
var secondBody: SKPhysicsBody
// 2. Assign the two physics bodies so that the one with the lower category is always stored in firstBody
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
// 3. react to the contact between ball and bottom
if firstBody.categoryBitMask == ballCatogary && secondBody.categoryBitMask == bottomWallCatogary {
//TODO: Replace the log statement with display of Game Over Scene
//add your code here.
}
}
And don't forget to add SKPhysicsContactDelegate at your class declaration and it will look like:
class playScene : SKScene, SKPhysicsContactDelegate {
//your code
}
If you want to detect another collision the you can do it this way:
if firstBody.categoryBitMask == ballCatogary && secondBody.categoryBitMask == objectsCatogary {
gameOver = 1
movingObjects.speed = 0
}
else if firstBody.categoryBitMask == objectsCatogary && secondBody.categoryBitMask == bottomWallCatogary{
score++
println(score)
}
Hope this will help.