ios - SpriteKit and Swift, changing picture of scrolling ground node while the game is running -

i have scrolling ground node in game player can jump , run on. how can change picture of ground node while game running? example, i'm spawning platforms periodically simple random number generator , if else condition spawns various platforms depending on number came number generator.

i want if number generator gives me number 4 picture of ground node changes water picture if touches water dies. code wrote picture of ground node wont change. i've tried this:

code ground node:

func initializingscrollingground() {     var index = 0; index < 2; index += 1 {         var ground = skspritenode(imagenamed: imagename)         ground.size = cgsize(width: frame.width, height: frame.height  / 6)         ground.position = cgpoint(x: index * int(ground.size.width), y: -30)         ground.zposition = 5         ground.anchorpoint = cgpointzero         ground.name = "ground"          let offsetx = ground.size.width * ground.anchorpoint.x         let offsety = ground.size.height * ground.anchorpoint.y          let path = cgpathcreatemutable()          cgpathmovetopoint(path, nil, 0 - offsetx, 48 - offsety)         cgpathaddlinetopoint(path, nil, 0 - offsetx, 0 - offsety)         cgpathaddlinetopoint(path, nil, 655 - offsetx, 0 - offsety)         cgpathaddlinetopoint(path, nil, 668 - offsetx, 48 - offsety)          cgpathclosesubpath(path)          ground.physicsbody = skphysicsbody(polygonfrompath: path)         ground.physicsbody?.categorybitmask = physicscatagory.ground         ground.physicsbody?.collisionbitmask = physicscatagory.player         ground.physicsbody?.contacttestbitmask = physicscatagory.player         ground.physicsbody?.affectedbygravity = false         ground.physicsbody?.dynamic = false          self.addchild(ground)     } }  func moveground() {     self.enumeratechildnodeswithname("ground", usingblock: { (node, stop) -> void in         if let ground = node as? skspritenode {             ground.position = cgpoint(x: ground.position.x - self.groundvelocity, y: ground.position.y)              // checks if ground node scrolled off screen, if yes, puts @ end of other node.             if ground.position.x <= -ground.size.width {                 ground.position = cgpointmake(ground.position.x + ground.size.width * 2, ground.position.y)             }         }     }) } 

code random number generator:

func dicerollplatforms() {     let diceroll = arc4random_uniform(4) + 1;      if diceroll == 1 {         // normal platforms         imagename = "ground_layer"         platforms_1()     }      if diceroll == 2 {         // normal platforms         imagename = "ground_layer"         platforms_2()     }      if diceroll == 3 {         // normal platforms         imagename = "ground_layer"         platforms_3()     }      if diceroll == 4 {         // platforms water beneath them         imagename = "water_layer"         platformswithwater()     } } 

there old discussion how handle kind of events. agree way of thinking sees wrong use of update method. why? because function called automatically 60 times per second (if it's possible) should fight counters, booleans and/or dispatch_once fire event in specific time.

the timers.

in sprite-kit bad way trigger event in time timer:

+ (nstimer *)scheduledtimerwithtimeinterval:(nstimeinterval)ti target:(id)atarget selector:(sel)aselector userinfo:(nullable id)userinfo repeats:(bool)yesorno 

in fact , opinion , according answer of learncocos2d here in sprite-kit must stay away : nstimer, performselector:afterdelay: , grand central dispatch because these timing methods ignore node's, scene's or view's paused state.

if want make timer in sprite-kit can use skaction. don't runblock, have thought extension.

code: swift 2.x , swift 3.x

extension skaction {     class func scheduledtimerwithtimeinterval(time:nstimeinterval, selector: selector,withobject: anyobject = sknode(), repeats:bool)->skaction {         // instead of nstimer use skactions         let call = skaction.customactionwithduration(0.0) { node, _ in             node.performselectoronmainthread(selector, withobject: withobject, waituntildone:false)         }         let wait = skaction.waitforduration(time)         let seq = skaction.sequence([wait,call])         let callselector = repeats ? skaction.repeatactionforever(seq) : seq         return callselector     } } 

// swift3

extension skaction {     class func scheduledtimerwithtimeinterval(time:timeinterval, selector: selector,withobject: anyobject = sknode(), repeats:bool)->skaction {         // instead of nstimer use skactions         let call = skaction.customaction(withduration: 0.0) { node, _ in             node.performselector(onmainthread: selector, with: withobject, waituntildone: false)         }         let wait = skaction.wait(forduration: time)         let seq = skaction.sequence([wait,call])         let callselector = repeats ? skaction.repeatforever(seq) : seq         return callselector         } } 

usage:

let time = 10.0 // or can generate random time let changeblocktimer = skaction.scheduledtimerwithtimeinterval(time, selector: #selector(gamescene.dicerollplatforms), repeats: true) self.runaction(changeblocktimer,withkey: "changeblocktimer")  // stop self.removeactionforkey("changeblocktimer") 

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if want increase randomness of events can use function in code:

code:

func randombool() -> bool {     return arc4random_uniform(2) == 0 ? true: false } 

usage:

if randombool() {    // give special gift enemies (shield, strong arms..) }