iOS 打开/关闭闪光灯

闪光灯的操作，在扫描二维码的时候需要用到

/// import AVFoundation.AVCaptureDevice

func toggleTorch(on: Bool) {
    guard
        let device = AVCaptureDevice.default(for: AVMediaType.video),
        device.hasTorch
    else { return }

    do {
        try device.lockForConfiguration()
        device.torchMode = on ? .on : .off
        // Optional thing you may want when the torch it's on, is to manipulate the level of the torch
        if on {
            try device.setTorchModeOn(level: AVCaptureDevice.maxAvailableTorchLevel.significand)
        }
        device.unlockForConfiguration()
    } catch {
        print("Torch could not be used")
    }
}