FatController.swift

import AVFoundation
import UIKit

class ScanViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
  var captureSession: AVCaptureSession!
  var previewLayer: AVCaptureVideoPreviewLayer!
  
  var previousScannedValue: String?
  
  override func viewDidLoad() {
    super.viewDidLoad()
    
    captureSession = AVCaptureSession()
    
    let videoCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    let videoInput: AVCaptureDeviceInput
    
    do {
      videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
    } catch {
      return
    }
    
    if (captureSession.canAddInput(videoInput)) {
      captureSession.addInput(videoInput)
    } else {
      failed();
      return
    }
    
    let metadataOutput = AVCaptureMetadataOutput()
    
    if (captureSession.canAddOutput(metadataOutput)) {
      captureSession.addOutput(metadataOutput)
      
      metadataOutput.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
      metadataOutput.metadataObjectTypes = [AVMetadataObjectTypeQRCode]
    } else {
      failed()
      return
    }
    
    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer.frame = view.layer.bounds
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
    view.layer.addSublayer(previewLayer)
    
    captureSession.startRunning()
  }
  
  func failed() {
    print("Failed")
  }
  
  override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    
    if (captureSession?.running == false) {
      captureSession.startRunning();
    }
  }
  
  override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    
    navigationController?.setNavigationBarHidden(true, animated: true)
  }
  
  override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    
    if (captureSession?.running == true) {
      captureSession.stopRunning();
    }
  }
  
  func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
    if let metadataObject = metadataObjects.first {
      let readableObject = metadataObject as! AVMetadataMachineReadableCodeObject;
      
      if readableObject.stringValue == previousScannedValue {
        return
      } else {
        AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
        foundCode(readableObject.stringValue);
        
        previousScannedValue = readableObject.stringValue
      }
    }
  }
  
  func foundCode(code: String) {
    print(code)
  }
  
  override func prefersStatusBarHidden() -> Bool {
    return true
  }
  
  override func supportedInterfaceOrientations() -> UIInterfaceOrientationMask {
    return .Portrait
  }
}