这是我的一个项目的工作示例，用于获取前置摄像头。这是在Objective-C中实现的，但事实证明它是可行的，并且足够容易转换为快捷方式。

NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
AVCaptureDevice *captureDevice = nil;

for (AVCaptureDevice *device in videoDevices){

    if (device.position == AVCaptureDevicePositionFront){

        captureDevice = device;
        break;
    }
}

在Swift 3.2+中：

if let videoDevices = AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo) {
    var captureDevice: AVCaptureDevice
    for device in videoDevices {
        if let device = device as? AVCaptureDevice {
            if device.position == AVCaptureDevicePosition.front {
                captureDevice = device
                break
            }
        }
    }
}