这里对于扫描功能不会过多的说明，毕竟只是一个小笔记而已。

简单的记录扫描所需部件：

/**

• 会话对象
  */
  -(AVCaptureSession *)session
  {
  if (!_session) {
  _session = [AVCaptureSession new];
  [_session setSessionPreset: AVCaptureSessionPresetHigh]; //高质量采集
  [self setupIODevice];
  }
  return _session;
  }

/**

• 视频输入设备
  */

• (AVCaptureDeviceInput *)input
  {
  if (!_input) {
  AVCaptureDevice * device = [AVCaptureDevice defaultDeviceWithMediaType: AVMediaTypeVideo];
  _input = [AVCaptureDeviceInput deviceInputWithDevice: device error: nil];
  }
  return _input;
  }

/**

• 数据输出对象
  */
  -(AVCaptureMetadataOutput *)output
  {
  if (!_output) {
  _output = [AVCaptureMetadataOutput new];
  [_output setMetadataObjectsDelegate: self queue: dispatch_get_main_queue()];
  }
  return _output;
  }

/**

• 扫描视图
  */
  -(AVCaptureVideoPreviewLayer *)scanView
  {
  if (!_scanView) {
  _scanView = [AVCaptureVideoPreviewLayer layerWithSession: self.session];
  _scanView.videoGravity = AVLayerVideoGravityResizeAspectFill;
  _scanView.frame = self.bounds;
  }
  return _scanView;
  }

/**

• 扫描范围
  */
  -(CGRect)scanRect
  {
  if (CGRectEqualToRect(_scanRect, CGRectZero)) {
  CGRect rectOfInterest = self.output.rectOfInterest;
  CGFloat yOffset = rectOfInterest.size.width - rectOfInterest.origin.x;
  CGFloat xOffset = 1 - 2 * SCANSPACEOFFSET;
  _scanRect = CGRectMake(rectOfInterest.origin.y * SCREENWIDTH, rectOfInterest.origin.x * (SCREENHEIGHT-NAV_BAR_HEIGHT), xOffset * SCREENWIDTH, yOffset * (SCREENHEIGHT-NAV_BAR_HEIGHT));
  }
  return _scanRect;
  }

主要的代理方法AVCaptureMetadataOutputObjectsDelegate

/**

• 二维码扫描数据返回
  */
  -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
  {
  if (metadataObjects.count > 0) {
  [self stop];
  AVMetadataMachineReadableCodeObject * metadataObject = metadataObjects[0];
  这里你将metadataObject.stringValue获取的字符串返回即可
  }}

/**

• 二维码扫描时获取光度来判断是否需要打开闪关灯
  */
  -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
  {
  CFDictionaryRef metadataDict = CMCopyDictionaryOfAttachments(NULL,sampleBuffer, kCMAttachmentMode_ShouldPropagate);
  NSDictionary metadata = [[NSMutableDictionary alloc] initWithDictionary:(__bridge NSDictionary)metadataDict];
  CFRelease(metadataDict);
  NSDictionary *exifMetadata = [[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary] mutableCopy];
  float brightnessValue = [[exifMetadata objectForKey:(NSString *)kCGImagePropertyExifBrightnessValue] floatValue];
  NSLog(@"%f",brightnessValue);//这里获取的就是外部环境的光度，你可以根据的光度的大小来进行判断是否需要打开闪关灯，值越大越亮
  // 根据brightnessValue的值来打开和关闭闪光灯
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
  BOOL result = [device hasTorch];// 判断设备是否有闪光灯
  if ((brightnessValue < 0) && result) {// 打开闪光灯
  [device lockForConfiguration:nil];
  [device setTorchMode: AVCaptureTorchModeOn];//
  [device unlockForConfiguration];
  }else if((brightnessValue > 0) && result) {// 关闭闪光灯
  [device lockForConfiguration:nil];
  [device setTorchMode: AVCaptureTorchModeOff];//关
  [device unlockForConfiguration];
  }
  }

最后给出Appledeveloper文档部分：https://developer.apple.com/documentation/coremedia/cmattachment?language=objc