swfit5 打开手电筒

 @objc func toggleTorch(on: Bool) {
        guard let device = AVCaptureDevice.default(for: AVMediaType.video) else { return }
        guard device.hasTorch else { print("Torch isn't available"); 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) }
            device.unlockForConfiguration()
        } catch {
            print("Torch can't be used")
        }
    }