iOS 相机超广角0.5x，1x，2x

需求：使用相机的广角功能，0.5x，1x，2x
代码：

AVCaptureDevice *backFacingCamera = nil;
    if (@available(iOS 13.0, *)) {
        AVCaptureDeviceDiscoverySession * session = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:@[AVCaptureDeviceTypeBuiltInTripleCamera, AVCaptureDeviceTypeBuiltInTrueDepthCamera, AVCaptureDeviceTypeBuiltInDualWideCamera, AVCaptureDeviceTypeBuiltInDualCamera, AVCaptureDeviceTypeBuiltInUltraWideCamera, AVCaptureDeviceTypeBuiltInTelephotoCamera, AVCaptureDeviceTypeBuiltInWideAngleCamera] mediaType:AVMediaTypeVideo position:currentCameraPosition];
        
        NSArray *devices = session.devices;
        for (AVCaptureDevice *device in devices) {
            //AVCaptureDeviceTypeBuiltInDualWideCamera
            if ([device position] == currentCameraPosition) {
                backFacingCamera = device;
                break;
            }
            NSLog(@"=======%@",device.deviceType);
        }
        
      NSArray *array = backFacingCamera.virtualDeviceSwitchOverVideoZoomFactors;
        NSLog(@"======%@  %f",array, backFacingCamera.dualCameraSwitchOverVideoZoomFactor);
        
    } else {
        NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
        for (AVCaptureDevice *device in devices)
        {
            if ([device position] == currentCameraPosition)
            {
                backFacingCamera = device;
            }
        }
    }

设置焦距

[_captureSession beginConfiguration];
[backFacingCamera setVideoZoomFactor:1];
 [_captureSession commitConfiguration];