SpriteKit：'String'不能转换为'DictionaryIndex <String，SKTexture>'

Question

同时编程SKAction.animateWithTextures（...）我遇到了这个错误（'String'is不能转换为'DictionaryIndex'）当我使用我的“状态”的字符串键来检索SKTexture相关。有人可以解释什么可能是错误的原因？

import SpriteKit 

class Player { 
    let states: Dictionary<String, SKTexture> = [ 
     "standing": SKTexture(imageNamed: "standing"), 
     "right1": SKTexture(imageNamed: "right1"), 
     "right2": SKTexture(imageNamed: "right2"), 
     "right3": SKTexture(imageNamed: "right3"), 
     "left1": SKTexture(imageNamed: "left1"), 
     "left2": SKTexture(imageNamed: "left2"), 
     "left3": SKTexture(imageNamed: "left3") 
    ] 

    let LEFT: UInt32 = 1 << 0 
    let FRONT: UInt32 = 1 << 1 
    let RIGHT: UInt32 = 1 << 2 

    var node: SKSpriteNode! 
    var status: UInt32! 

    let delay = SKAction.waitForDuration(NSTimeInterval(0.1)) 

    var runLeft: SKAction! 
    var runRight: SKAction! 

    init(){ 
     for state in states { 
      state.1.filteringMode = .Nearest 
     } 

     node = SKSpriteNode(texture: states["standing"]) 

     node.physicsBody = SKPhysicsBody(rectangleOfSize: node.size) 
     node.physicsBody.dynamic = false 

     status = FRONT 

     runLeft = SKAction.animateWithTextures([states["left1"], states["left2"], states["left1"], states["left3"]]!, timePerFrame: 0.1) 
     runRight = SKAction.animateWithTextures([states["right1"], states["right2"], states["right1"], states["right3"]]!, timePerFrame: 0.1) 
    } 
} 

Answer 1

词典查找返回选项，因为该键可能不存在。你需要解开每一个查找，因为他们是SKTexture!：

runLeft = SKAction.animateWithTextures([states["left1"]!, states["left2"]!, states["left1"]!, states["left3"]!], timePerFrame: 0.1) 
    runRight = SKAction.animateWithTextures([states["right1"]!, states["right2"]!, states["right1"]!, states["right3"]!], timePerFrame: 0.1)