init() is unavailable in AVCaptureDeviceInput in Swift 4

Question

I have a view controller in my application that shows the back camera like Snapchat and it was worked well in Swift 3, but when I updated to Swift 4, the compiler won't let me run it because of the following error:

init() is unavailable for AVCaptureDeviceInput

This view controller should show the camera without any button or extra things just like Snapchat. So, here is the full view controller code:

import UIKit
import AVFoundation

class cameraViewController: UIViewController , UIImagePickerControllerDelegate , UINavigationControllerDelegate {

var captureSession : AVCaptureSession?

var stillImageOutput : AVCaptureStillImageOutput?

var previewLayer : AVCaptureVideoPreviewLayer?

var imagePicker: UIImagePickerController!

@IBOutlet weak var cameraView: UIView!

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    previewLayer?.frame = cameraView.bounds
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)


    captureSession = AVCaptureSession()

    captureSession?.sessionPreset = AVCaptureSessionPreset1280x720

    let backCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)

    let error : NSError?

    var input = AVCaptureDeviceInput()

    do {
        input = try AVCaptureDeviceInput(device: backCamera)
    }
    catch {
        //  error
    }

    if error == nil && (captureSession?.canAddInput(input))! {

        captureSession?.addInput(input)

        stillImageOutput = AVCaptureStillImageOutput()

        stillImageOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecJPEG]


        if (captureSession?.canAddOutput(stillImageOutput))! {

            captureSession?.addOutput(stillImageOutput)

            previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

            previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill

            previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait

            cameraView.layer.addSublayer(previewLayer!)

            captureSession?.startRunning() 

        }
    }

}

}

I can't run the application because of this line:

var input = AVCaptureDeviceInput()

Answer 1

so I used all of the left codes inside do catch and I got the result and the app is working well in the swift 4 - so instead of view will appear in my question codes use this codes below

 override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)


    captureSession = AVCaptureSession()

    captureSession?.sessionPreset = AVCaptureSessionPreset1280x720


    do {
        let input = try AVCaptureDeviceInput(device: .defaultDevice(withMediaType: AVMediaTypeVideo))

        captureSession?.addInput(input)

        stillImageOutput = AVCaptureStillImageOutput()

        stillImageOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecJPEG]


        if (captureSession?.canAddOutput(stillImageOutput))! {

            captureSession?.addOutput(stillImageOutput)

            previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

            previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill

            previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait

            cameraView.layer.addSublayer(previewLayer!)

            captureSession?.startRunning()

        }



    } catch {

        print(error)

    }

}

I have answered my question to help other people