title: Type of "SCNAudioSource *_steps[StepsSoundCount][AAPLFloorMaterialCount]"
body: <p>I found this interesting line of code in WWDC 15 Fox project,file APPLCharacter.m.Please just tell me the type,IDK much objective-c
  <code> SCNAudioSource *_steps[StepsSoundCount][AAPLFloorMaterialCount];</code>
  Here is the enum
  <code>typedef NS_ENUM(NSUInteger, AAPLFloorMaterial) {
      AAPLFloorMaterialGrass,
      AAPLFloorMaterialRock,
      AAPLFloorMaterialWater,
      AAPLFloorMaterialInTheAir,
      AAPLFloorMaterialCount
  };</code>and
  <code>#define StepsSoundCount 10</code></p>
  
  <p>What type is _steps ?
  How can this be translated into swift ?</p>