Depreciated Code from Swift 2 to Swift 3 - xcode

Question

So I followed this tutorial on youtube: https://www.youtube.com/watch?v=uUTevJAhL3Q, and I can't figure out how to update the rest to Swift 3; I am relatively new at Swift and still learning, if anyone could help me out a bit that would be fantastic! I am trying to re-create a snapchat camera-view.
import UIKit
import AVFoundation
class CameraVC: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
var captureSession : AVCaptureSession?
var stillImageOutput : AVCaptureStillImageOutput?
var previewLayer : AVCaptureVideoPreviewLayer?
#IBOutlet var cameraView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
previewLayer?.frame = cameraView.bounds
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
captureSession = AVCaptureSession()
captureSession?.sessionPreset = AVCaptureSessionPreset1920x1080
var backCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
var error : NSError?
var input = AVCaptureDeviceInput(device: backCamera, error: &error)
if (error == nil && captureSession?.canAddInput(input) != nil){
captureSession?.addInput(input)
stillImageOutput = AVCaptureStillImageOutput()
stillImageOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecJPEG]
if (captureSession?.canAddOutput(stillImageOutput) != nil){
captureSession?.addOutput(stillImageOutput)
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait
cameraView.layer.addSublayer(previewLayer!)
captureSession?.startRunning()
}
}
}
#IBOutlet var tempImageView: UIImageView!
func didPressTakePhoto(){
if let videoConnection = stillImageOutput?.connection(withMediaType: AVMediaTypeVideo){
videoConnection.videoOrientation = AVCaptureVideoOrientation.portrait
stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler: {
(sampleBuffer, error) in
if sampleBuffer != nil {
var imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer)
var dataProvider = CGDataProvider(data: imageData as! CFData)
var cgImageRef = CGImage(jpegDataProviderSource: dataProvider, decode: nil, shouldInterpolate: true, intent: kCGRenderingIntentDefault)
var image = UIImage(CGImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.Right)
self.tempImageView.image = image
self.tempImageView.isHidden = false
}
})
}
}
var didTakePhoto = Bool()
func didPressTakeAnother(){
if didTakePhoto == true{
tempImageView.isHidden = true
didTakePhoto = false
}
else{
captureSession?.startRunning()
didTakePhoto = true
didPressTakePhoto()
}
}
func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
didPressTakeAnother()
}
}

Answer 1

Swift 3 introduced the idea of error handling and most (if not all) of Apple's Foundation and Core APIs got updated so that instead of using capturing an error with the inout &error parameter the method throws and error.
So code that you used to write like this:
var error : NSError?
var input = AVCaptureDeviceInput(device: backCamera, error: &error)
In Swift 3 is updated to drop the error parameter, and you use the new do, try, catch syntax:
do {
var input = try AVCaptureDeviceInput(device: backCamera)
//... input was assigned without an error, you can use in the scope of this statement
}
catch {
// an error occured attempting `AVCaptureDeviceInput(device: backCamera)`
print("an error occured")
}
Of if you prefer, the shorthand versions:
var input = try! AVCaptureDeviceInput(device: backCamera)
// not safe: app will crash if AVCaptureDeviceInput fails
var input = try? AVCaptureDeviceInput(device: backCamera)
// safer: input will be assigned as `nil` if AVCaptureDeviceInput fails
Next time you're converting from Swift 2 to Swift 3, try using Xcode's 'refactor' tool it does a pretty good job of automatically making these changes for you.