swift - Could not cast value of type 'SCNView' to 'SKView' -

i'm following tutorial create "tetris" game in swift xcode 7. followed every single step in tutorial, i'm getting runtime error:

could not cast value of type 'scnview' (0x106c19778) 'skview' (0x1068fcad0).

my gameviewcontroller.swift follows:

import uikit import scenekit import spritekit  class gameviewcontroller: uiviewcontroller {      var scene: gamescene!     var swiftris:swiftris!      override func viewdidload() {         super.viewdidload()          //configure view         let skview = view as! skview          skview.multipletouchenabled = false         //create , configure scene         scene = gamescene(size: skview.bounds.size)         scene.scalemode = .aspectfill         scene.tick = didtick         swiftris = swiftris()         swiftris.begingame()          //presente scene.         skview.presentscene(scene)          scene.addpreviewshpaetoscene(swiftris.nextshape!){             self.swiftris.nextshape?.moveto(startingcolumn, row: startingrow)             self.scene.movepreviewshape(self.swiftris.nextshape!){                 let nextshapes = self.swiftris.newshape()                 self.scene.startticking()                 self.scene.addpreviewshpaetoscene(nextshapes.nextshape!) {}             }         }     }      override func prefersstatusbarhidden() -> bool {              return true        }      func didtick(){         swiftris.fallingshape?.lowershapebyonerow()         scene.redrawshape(swiftris.fallingshape!, completion: {})     } } 

i search on google , here , didn`t find related scnview , skview.

thank in advance.

i did find problem code. instantiate skview view inside gameviewcontroller:

self.view = skview()     let skview = view as! skview 

before that, tried change class of view skview in storyboard, not possible.

i'd thank revisions.