Swift Decodable 找不到key時，使用預設值

使用JSONDecoder時，如果找不到Key值，錯誤如下

▿ DecodingError
  ▿ keyNotFound : 2 elements
    - .0 : CodingKeys(stringValue: "b", intValue: nil)
    ▿ .1 : Context
      - codingPath : 0 elements
      - debugDescription : "No value associated with key CodingKeys(stringValue: \"b\", intValue: nil) (\"b\")."
      - underlyingError : nil

其實只要利用KeyedDecodingContainer的decode(type:forKey)就可以解決這問題

protocol Init {
    init()
}

extension KeyedDecodingContainer {
    func decode<T: Codable & Init>(_ type: T.Type,
                forKey key: Key) throws -> T {
        try decodeIfPresent(type, forKey: key) ?? .init()
    }
}

之後只要將Codable後面，加上Init這個protocal就可以了

enum B: Int, Codable {
    case one = 1
    case two = 2
}


extension B: Init {
    init() {
        self = .one
    }
}

用swift讀寫NTag

1. 在info.plist中，加入Privacy - NFC Scan Usage Description
2. 在Capabilities 加入Near Field Communication Tag Reading
   
3. 掃描

   func startScan() {

           let session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: false)

           session.alertMessage = "Hold your iPhone near an NFC transit card."

           session.begin()

   }

4. 連線，更新payload

   func readerSession(_ session: NFCNDEFReaderSession, didDetect tags: [NFCNDEFTag]) {

       guard

           let sms = "場所代碼：111111111111111 本次實聯簡訊限防疫目的使用。".addingPercentEncoding(withAllowedCharacters: .urlHostAllowed),

           let payload = NFCNDEFPayload.wellKnownTypeURIPayload(string: "sms:1922&body=\(sms)"),

           let tag = tags.first

       else {

           session.invalidate(errorMessage: "Could not process tag.")

           return

       }

       session.connect(to: tag) { error in

           guard error == nil else {

               session.invalidate(errorMessage: "Could not connect to tag.")

               return

           }

           tag.queryNDEFStatus { status, capacity, error in

               guard error == nil else {

                   session.invalidate(errorMessage: "Could not query status of tag.")

                   return

               }

               

               switch status {

               case .notSupported:

                   session.invalidate(errorMessage: "Tag is not supported.")

               case .readOnly:

                   session.invalidate(errorMessage: "Tag is only readable.")

               case .readWrite:

                   let messge = NFCNDEFMessage.init(records: [payload])

                   tag.writeNDEF(messge) { error in

                       if error != nil {

                           session.invalidate(errorMessage: "Failed to write message.")

                       } else {

                           session.alertMessage = "Successfully configured tag."

                           session.invalidate()

                       }

                   }

                   

               @unknown default:   session.invalidate(errorMessage: "Unknown status of tag.")

               }

           }

       }

   }

PS.找不到 Near Field Communication Tag Reading ，請切換開發者帳號到付費帳號

ARKit(SpriteKit) 臉部角度追蹤

1. 建立😘 。由於前鏡頭左右相反，所以X軸要反向。

   let labelNode = SKLabelNode(text: "😘")

   labelNode.horizontalAlignmentMode = .center

   labelNode.verticalAlignmentMode = .center

   labelNode.xScale = -1

2. 須將😘放入SKTransformNode，做後續的3D轉換。
   

   let face = SKTransformNode()

   face.addChild(labelNode)

   self.face = face

3. 更新時，SKTransformNode再依據ARFaceAnchor旋轉
   

   let rotate = faceAnchor.transform.rotate

   face?.setRotationMatrix(rotate)

4. 最後，記得將node轉回來，否則貼圖會是反的

完整程式

ARKit(SceneKit) 更新模型臉部表情

ARKit(SceneKit) 臉部貼圖

1. 修改Tracking and Visualizing Faces範例中的貼圖『wireframeTexture.png』
2. 指定ARSCNFaceGeometry的貼圖

   faceMesh?.firstMaterial?.diffuse.contents = UIImage(named: "wireframeTexture")

ARKit(SceneKit) 臉部表情追蹤

1.  建立臉部追蹤

// Create a session configuration

 let configuration = ARFaceTrackingConfiguration()

// Run the view's session

sceneView.session.run(configuration)

2.  建立臉部模型

func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {

    if anchor is ARFaceAnchor {

        let faceMesh = ARSCNFaceGeometry(device: sceneView.device!)

        faceMesh?.firstMaterial?.lightingModel = .physicallyBased

        let node = SCNNode(geometry: faceMesh)

        return node

    } else {

        return nil

    }

}

3.  更新臉部表情

func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {

    if let faceAnchor = anchor as? ARFaceAnchor, let faceGeometry = node.geometry as? ARSCNFaceGeometry {

        faceGeometry.update(from: faceAnchor.geometry)

    }

}

RealityKit 判斷手指觸摸物件

1. 用Reality Composer編輯物件『屬性』，勾選『物理效果』『加入』
2. 將ARFrame.capturedImage轉成CVPixelBuffer

   func session(_ session: ARSession, didUpdate frame: ARFrame) {

           guard let arView = arView else {return}

           // Do not enqueue other buffers for processing while another Vision task is still running.

           // The camera stream has only a finite amount of buffers available; holding too many buffers for analysis would starve the camera.

           guard currentBuffer == nil, case .normal = frame.camera.trackingState else {

               return

           }

           // Retain the image buffer for Vision processing.

           let currentBuffer = frame.capturedImage

   }

3. 利用Vision偵測食指
   

   let requestHandler = VNImageRequestHandler(cvPixelBuffer: currentBuffer, orientation: orientation)

   visionQueue.async {

           do {

                   // Perform VNDetectHumanHandPoseRequest

                   try requestHandler.perform([self.handPoseRequest])

                   // Continue only when a hand was detected in the frame.

                   // Since we set the maximumHandCount property of the request to 1, there will be at most one observation.

                   guard let observation = self.handPoseRequest.results?.first else {

                       return

                   }

                   // Get points for index finger.

                   let indexFingerPoints = try observation.recognizedPoints(.indexFinger)

                   // Look for tip points.

                   guard let indexTipPoint = indexFingerPoints[.indexTip] else {

                       return

                   }

                   // Ignore low confidence points.

                   guard indexTipPoint.confidence > 0.3 else {

                       return

                   }

                   

                   

           } catch {

                   print("Error: Vision request failed with error \"\(error)\"")

           }

   }

4. 將Vision的座標轉成ARView的座標
   

   // Convert points from Vision coordinates to ARView coordinates.

   let point = indexTipPoint.location

   let tip = CGPoint(x: point.x * width, y: (1 - point.y) * height)

sample code

RealityKit 判斷物件點擊方法2

1. 用Reality Composer編輯物件『屬性』，勾選『物理效果』『加入』
2. 替arView加上手勢功能
   

   arView.addGestureRecognizer(

         UITapGestureRecognizer(

               target: xxxx,

               action: #selector(XXXX.handleTap(recognizer:))

       )

   )

3. 
   

   @objc func handleTap(recognizer: UITapGestureRecognizer) {

           let tapLocation = recognizer.location(in: arView)

           let entity = arView.entity(at: tapLocation)

           guard entity == boxAnchor?.steelBox else { return }

           // entity 即點擊物件

   }

RealityKit 判斷物件點擊方法1

 直接用Reality Composer編輯物件行為

1. 選取物件
2. 顯示行為(⌥⌘B)
3. 加入行為『點按與反轉』