You need to make explicit Objective-C reference: @objc
@objc func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
let chosenImage = info[UIImagePickerControllerOriginalImage] as! UIImage
image = chosenImage
self.performSegue(withIdentifier: "ShowEditView", sender: self)
dismiss(animated: true, completion: nil)
}