Turn On/Off Video Camera Torch

turn-on-off-video-camera-torch.swift

/*
Step 1 - Privacy Text for Requesting Camera Permission

Open the Info.plist file as source code and enter the following text in the <dict></dict>:

<key>NSCameraUsageDescription</key>
<string>This app requires camera</string>
*/

// Step 2 - Imports
import AVFoundation

// Step 3 - Check for Camera Permission
let status = AVCaptureDevice.authorizationStatus(for: .video)
switch status {
case .authorized: print("authorized")
case .notDetermined: return .notRequested
default: return .unauthorized
}

// Step 4 - Request for Camera Permission
AVCaptureDevice.requestAccess(for: .video) { granted in
    DispatchQueue.main.async {
        guard granted else {
            print("permission not granted")
            return
        }
        print("authorized")
    }
}

// Step 5 - Get Back Camera Capture Device
func getBackVideoCaptureDevice() -> AVCaptureDevice? {
    if let tripleCamera = AVCaptureDevice.default(.builtInTripleCamera, for: .video, position: .back) {
        return tripleCamera
    }
    if let dualWideCamera = AVCaptureDevice.default(.builtInDualWideCamera, for: .video, position: .back) {
        return dualWideCamera
    }
    if let dualCamera = AVCaptureDevice.default(.builtInDualCamera, for: .video, position: .back) {
        return dualCamera
    }
    if let wideAngleCamera = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back) {
        return wideAngleCamera
    }
    return nil
}

// Step 6 - Get Camera Capture Device Input
func getCaptureDeviceInput(captureDevice: AVCaptureDevice) -> AVCaptureDeviceInput? {
    do {
        let captureDeviceInput = try AVCaptureDeviceInput(device: captureDevice)
        return captureDeviceInput
    } catch let error {
        print("Failed to get capture device input with error \(error)")
    }
    return nil
}

// Step 7 - Add Camera Capture Device Input to Capture Session
let captureSession: AVCaptureSession
if let videoCaptureDevice = getBackVideoCaptureDevice() {
    if let videoCaptureDeviceInput = getCaptureDeviceInput(captureDevice: videoCaptureDevice) {
        if captureSession.canAddInput(videoCaptureDeviceInput) {
            captureSession.addInput(videoCaptureDeviceInput)
        }
    }
}

// Step 8 - Is Torch Available
// Only the back camera has torch
// Torch becomes unavailable when the device overheats
var isTorchAvailable: Bool {
    guard let videoCaptureDevice = videoCaptureDevice else { return false }
    guard videoCaptureDevice.hasTorch else { return false }
    return videoCaptureDevice.isTorchAvailable
}

// Step 9 - Setup Key-Value Observing for Torch Available
// We setup KVO to monitor status of torch available
// When device cools down, torch becomes available
// And torch is unavailable when device overheats
func setupKVOForTorchAvailable() {
    guard let videoCaptureDevice = videoCaptureDevice else { return }
    guard videoCaptureDevice.hasTorch else { return }
    let _ = videoCaptureDevice.observe(\.isTorchAvailable, options: [.new]) { captureDevice, change in
        if change.newValue == true {
            print("torch is available")
        } else {
            print("torch is unavailable")
        }
    }
}

// Step 10 - Turn On/Off Video Camera Torch
func setTorchMode(torchMode: AVCaptureDevice.TorchMode) -> Bool {
    guard let videoCaptureDevice = videoCaptureDevice else { return false }
    do {
        try videoCaptureDevice.lockForConfiguration()
    } catch let error as NSError {
        print("failed to get lock for configuration on capture device with error \(error)")
    }
    guard videoCaptureDevice.isTorchAvailable else { return false }
    videoCaptureDevice.torchMode = torchMode
    videoCaptureDevice.unlockForConfiguration()
    return true
}
let status = setTorchMode(torchMode: .on) // turning on torch
let status = setTorchMode(torchMode: .off) // turning off torch

// Step 11 - Remove Video Capture Device Input
captureSession.removeInput(videoCaptureDeviceInput)