Several errors in my Swift code for a camera app - swift

Question

I am trying to create a camera app on Xcode 10.1 using Swift for a school project. I have been working on this for a while, and still have several errors.
import UIKit
import AVFoundation
class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
let captureSession = AVCaptureSession()
var previewLayer:CALayer!
var captureDevice:AVCaptureDevice?
var takePhoto = false
override func viewDidLoad() {
super.viewDidLoad()
prepareCamera()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
prepareCamera()
}
func prepareCamera() {
captureSession.sessionPreset = AVCaptureSession.Preset.photo
if let availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [AVCaptureDevice.builtInWideAngleCamera], mediaType: AVMediaType.video, position: AVCaptureDevice.back) {
//if availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType:AVMediaType.video, position: .back).devices {
//let captureDevice = availableDevices
beginSession()
}
}
func beginSession () {
do {
let captureDeviceInput = try AVCaptureDeviceInput( device: captureDevice)
captureSession.addInput(captureDeviceInput)
} catch {
print(error.localizedDescription)
}
if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
self.previewLayer = previewLayer
self.view.layer.addSublayer(self.previewLayer)
self.previewLayer.frame = self.view.layer.frame
captureSession.startRunning()
let dataOutput = AVCaptureVideoDataOutput()
dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString): NSNumber(value: kCVPixelFormatType_32BGRA)] as [String : Any]
dataOutput.alwaysDiscardsLateVideoFrames = true
if captureSession.canAddOutput(dataOutput) {
captureSession.addOutput(dataOutput)
}
captureSession.commitConfiguration()
let queue = DispatchQueue(label: "com.sophiaradis.captureQueue")
dataOutput.setSampleBufferDelegate(self, queue: queue)
}
}
#IBAction func takePhoto(_ sender: Any) {
takePhoto = true
}
func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
if takePhoto {
takePhoto = false
if let image = self.getImageFromSamplyBuffer(buffer: sampleBuffer){
let photoVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "PhotoVC") as! PhotoViewController
photoVC.takenPhoto = image
DispatchQueue.main.async {
self.present(photoVC, animated: true, completion: {
self.stopCaptureSession()
})
}
}
}
}
func getImageFromSamplyBuffer (buffer:CMSampleBuffer) -> UIImage? {
if let pixelBuffer = CMSampleBufferGetImageBuffer(buffer) {
let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
let context = CIContext()
let imageRect = CGRect(x: 0, y: 0, width: CVPixelBufferGetWidth(pixelBuffer), height: CVPixelBufferGetHeight(pixelBuffer))
if let image = context.createCGImage(ciImage, from: imageRect) {
return UIImage(cgImage: image, scale: UIScreen.main.scale, orientation: .right)
}
}
return nil
}
func stopCaptureSession () {
self.captureSession.stopRunning()
if let inputs = captureSession.inputs as? [AVCaptureDeviceInput] {
for input in inputs {
self.captureSession.removeInput(input)
}
}
}
}
There is an error in these lines of code:
if let availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes:[AVCaptureDevice.builtInWideAngleCamera], mediaType: AVMediaType.video, position: AVCaptureDevice.back)
This error says that type AVCaptureDevice has no member Discovery Session. But when I looked online, it did.
There is a second error in these lines that follow that I cannot convert value of type 'AVCaptureDevice?' to expected argument type 'AVCaptureDevice'.
func beginSession () {
do {
let captureDeviceInput = try AVCaptureDeviceInput( device: captureDevice)
I have no idea how to fix this one at all. My next error occurs directly below that one, in these following lines
if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
self.previewLayer = previewLayer
self.view.layer.addSublayer(self.previewLayer)
self.previewLayer.frame = self.view.layer.frame
captureSession.startRunning()
And this is flagged as that Initializer for conditional binding must have Optional type, not 'AVCaptureVideoPreviewLayer'.
If you can fix or even offer advice as how to fix any of these it will mean a lot to me and really make my year.

Answer 1

1-
let availableDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera], mediaType: AVMediaType.video, position: AVCaptureDevice.Position.back)
2- if let captureDevice or force unwrap captureDevice!
let captureDeviceInput = try AVCaptureDeviceInput( device: captureDevice!)
3- AVCaptureVideoPreviewLayer doesn't return optional , so replace
if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
with
let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)