ios - Applying velocity to a SKSpriteNode subclass & trouble with Expected Declaration Error -

i'm working on first iphone game , have skspritenode subclass alien (which abstract class) later inherited class normalien. apple's docs, i've been having lot of trouble figuring out class initialization , inheritance in swift. here code both classes:

//generic alien type: blue-print of sorts class alien:skspritenode{      static func normalizevector(vector:cgvector) -> cgvector{         let len = sqrt(vector.dx * vector.dx + vector.dy * vector.dy)         return cgvector(dx:vector.dx / len, dy:vector.dy / len)     }      func motion(velocity:cgvector, multiplier:cgfloat){         //alien.physicsbody?.velocity.dx = velocity.dx * multiplier //why no work?         self.physicsbody?.velocity.dx = velocity.dx * multiplier         self.physicsbody?.velocity.dy = velocity.dy * multiplier     }      let velocityvector:cgvector     let startpos:cgpoint      init(texture:sktexture, startposition startpos:cgpoint,movespeed: cgfloat,velocityvector:cgvector){          self.velocityvector = alien.normalizevector(velocityvector)         self.startpos = startpos          //makes sure skspritenode initialized before modifying properties         super.init(texture: texture, color: uicolor.clearcolor(), size: texture.size())          //physicsbody property of super super.init must called first (init skspritenode)         self.physicsbody? = skphysicsbody(circleofradius: self.size.width/2)         self.physicsbody?.dynamic = true         self.physicsbody?.categorybitmask = physicscategory.alien //physicsbody?. optional chaining?         self.physicsbody?.collisionbitmask = 0 //do need this? or jsut use in laser class         self.physicsbody?.contacttestbitmask = physicscategory.laser         self.physicsbody?.usesprecisecollisiondetection = true          //motion         self.physicsbody?.velocity.dx = velocityvector.dx * movespeed         self.physicsbody?.velocity.dy = velocityvector.dy * movespeed          //self.velocityvector = normalizevector(velocityvector)         self.position = startpos     }      //alien.motion(self.velocityvector, movespeed)      required init?(coder adecoder: nscoder) {         fatalerror("init(coder:) has not been implemented")     }  } 

as as:

class normalien:alien{      static let alienimage = sktexture(imagenamed:"sprites/alien.png")     //alienimage.setscale(0.2)      init(startpos:cgpoint,speed: cgfloat){         super.init(texture:normalien.alienimage, startposition: startpos, movespeed:speed,velocityvector:cgvector(dx: 1,dy: 0))     }       required init?(coder adecoder: nscoder) {         fatalerror("init(coder:) has not been implemented")     } } 

i have function:

func buildalien(){      let aalien = normalien(startpos:cgpoint(x:0,y:size.height/2), speed:100)      addchild(aalien) } 

that instantiates normalien within didmovetoview (this function called within skaction.repeatactionforever). reason each sprite created fails move. i'm confused because move if use skaction.moveto must not understand applying velocity.

on top of this, i'm confused why receive error: expected declarationwhen attempt manipulate normaliens texture alienimage.setscale(0.2) , when try call internal method on class: alien.motion(self.velocityvector, movespeed)? think calling method inside class cause every instance make have called- making them potentially move.

any appreciated.