如何在ios開發中,使用相機時切換攝像頭

//先聲明兩個屬性,遵循兩個協議(協議可能非必要,視具體開發而定)
//    <AVCaptureVideoDataOutputSampleBufferDelegate,AVCaptureAudioDataOutputSampleBufferDelegate>
//    @property (nonatomic, strong) AVCaptureSession *captureSession;
//    @property (nonatomic, strong) AVCaptureDeviceInput *currentVideoDeviceInput;
   
   // 1.獲取當前設備方向
   AVCaptureDevicePosition curPosition = _currentVideoDeviceInput.device.position;
   
   // 2.獲取需要改變的方向
   AVCaptureDevicePosition togglePosition = curPosition == AVCaptureDevicePositionFront?AVCaptureDevicePositionBack:AVCaptureDevicePositionFront;
   
   // 3.獲取改變的攝像頭設備
   AVCaptureDevice *toggleDevice = [self getVideoDevice:togglePosition];
   
   // 4.獲取改變的攝像頭輸入設備
   AVCaptureDeviceInput *toggleDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:toggleDevice error:nil];
   
   // 5.移除之前攝像頭輸入設備
   [_captureSession removeInput:_currentVideoDeviceInput];
   
   // 6.添加新的攝像頭輸入設備
   [_captureSession addInput:toggleDeviceInput];
   
   // 7.記錄當前攝像頭輸入設備
   _currentVideoDeviceInput = toggleDeviceInput;