首先在 UploadImageView 繼承中加入 UIImagePickerController
class UploadImageView: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    
    var imagePicker: UIImagePickerController!
    
    ...
    
    override func viewDidLoad() {
        super.viewDidLoad()
        image.delegate = self
        imagePicker
    }
    
    
}

接著，把上傳動作指定給 Button

present(imagePickerBtn, animated: true, completion: nil)

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String: Any]) {
//將上傳的圖片轉成 UIImage
    if let image = info[UIImagePickerControllerOriginalImage] as? [UIImage] {
        
        iv_userImage.image = image
    }
    imagePicker.dismiss(animated: true, completion: nil)
}