swift - Swift：从 Firebase 检索数据并在表格视图中显示

Question

我正在制作一个具有图像新闻提要（HomeViewController）的应用程序。用户可以点击与SiteViewController连接的每个图像，该控制器具有空数据的表格视图和一个按钮，当单击该按钮时，该按钮将连接到ContextSheetViewController，用户可以在其中上传他们在新闻提要中单击的图像的数据。然后用户按下上传，这些数据（siteCodeTextView、areaCodeTextView、trenchTextView）被保存到 firebase 并返回到 SiteViewController。然后我想在 SiteViewController 的表视图中检索刚刚上传的图像的siteCodeTextView的数据值。但是当我在 ContextSheetViewController 中按下上传时，错误：在展开 Optional 值时意外发现 nil。而且我的sheetId在 SiteViewController 中打印 nil 所以我不确定如何正确检索它？有什么帮助吗？

这是我的相关视图控制器的故事板：

SiteViewController 的代码：

class SiteViewController: UIViewController {

    @IBOutlet weak var tableView: UITableView!


    var sheets = [Sheet]()
    var users = [User]()
    var sheetId: String!

    var postId: String!

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.dataSource = self
        loadSheets()

        print(postId)
        print(sheetId)
    }
    func loadSheets() {
        Api.Sheet.REF_SHEETS.child(self.postId!).observe(.childAdded, with: {
            snapshot in
            Api.Sheet.observeSheets(withSheetId: snapshot.key, completion: {
                sheet in
//                self.fetchUser(uid: sheet.uid!, completed: {
                    print("sheet id: \(sheet.id)")
                    print("sheet uid: \(sheet.uid)")
                self.sheets.append(sheet)
                self.tableView.reloadData()
//                })
            })
        })
    }

    func fetchUser(uid: String, completed:  @escaping () -> Void ) {

        Api.User.observeUser(withId: uid, completion: {
            user in
            self.users.append(user)
            completed()
        })
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "SheetSegue" {
            let sheetVC = segue.destination as! SheetViewController
            let sheetId = sender as! String
            sheetVC.sheetId = sheetId

        }
    }
}

extension SiteViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return sheets.count
    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "SheetCell", for: indexPath) as! SiteTableViewCell
        let sheet = sheets[indexPath.row]

        print("sheet id: \(sheet.id)")
        print("sheet uid: \(sheet.uid)")
//        let user = users[indexPath.row]
//        cell.user = user
        cell.sheet = sheet
        cell.delegate = self
        return cell
    }
}

extension SiteViewController: SiteTableViewCellDelegate {
    func goToSheetVC(sheetId: String) {
        performSegue(withIdentifier: "SheetSegue", sender: sheetId)

    }
}

ContextSheetViewController 的代码：

class ContextSheetViewController: UIViewController {


    @IBOutlet weak var siteCodeTextView: UITextField!
    @IBOutlet weak var areaCodeTextView: UITextField!
    @IBOutlet weak var trenchTextView: UITextField!
    @IBOutlet weak var uploadArtefactImage: UIImageView!

    @IBOutlet weak var artefactImageView: UIImageView!

    var selectedImage: UIImage?
    var postId: String!
    override func viewDidLoad() {
        super.viewDidLoad()
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(self.handleSelectPhoto))
        uploadArtefactImage.addGestureRecognizer(tapGesture)
        uploadArtefactImage.isUserInteractionEnabled = true

    }

    @objc func handleSelectPhoto() {
        let pickerController = UIImagePickerController()
        pickerController.delegate = self
        present(pickerController, animated: true, completion: nil)
    }

    @IBAction func uploadButton_TouchUpInside(_sender: Any) {

        if let profileImg = self.artefactImageView.image, let imageData = UIImageJPEGRepresentation(profileImg, 0.1) {
            let photoIdString = NSUUID().uuidString
            print(photoIdString)
            let storageRef = Storage.storage().reference(forURL: Config.STORAGE_ROOF_REF).child("sheets").child(photoIdString)
            storageRef.putData(imageData, metadata: nil, completion: { (metadata, error) in
                if error != nil {
                    ProgressHUD.showError(error!.localizedDescription)
                    return
                }
                let photoUrl = metadata?.downloadURL()?.absoluteString
                self.sendDataToDatabase(photoUrl: photoUrl!)
            })
        } else {
            ProgressHUD.showError("Sheet Image can not be empty!")
        }
    }

    func sendDataToDatabase(photoUrl: String) {
//        let ref = Database.database().reference()
        let sheetsReference = Api.Sheet.REF_SHEETS
//        let sheetsReference = ref.child("sheets")
        let newSheetId = sheetsReference.childByAutoId().key
        let newSheetReference = sheetsReference.child(newSheetId)
        guard let currentUser = Auth.auth().currentUser else {
            return
        }
        let currentUserId = currentUser.uid
        newSheetReference.setValue(["uid": currentUserId, "photoUrl": photoUrl, "siteCodeTextView": siteCodeTextView.text!, "areaCodeTextView": areaCodeTextView.text!, "trenchTextView": trenchTextView.text!], withCompletionBlock: {
            (error, ref) in
            if error != nil {
                ProgressHUD.showError(error!.localizedDescription)
                return
        }
            let postSheetRef = Api.Sheet.REF_SHEETS.child(self.postId!).child(newSheetId)
//            let postSheetRef = Api.Sheet.REF_SHEETS.child("post-sheets").child(self.postId).child(newSheetId)
            postSheetRef.setValue(true, withCompletionBlock: { (error, ref) in
                if error != nil {
                    ProgressHUD.showError(error!.localizedDescription)
                    return
                }
            })


            ProgressHUD.showSuccess("Success")
            self.clean()
            self.navigationController?.popViewController(animated: true)
        })
    }

    func clean() {
        self.siteCodeTextView.text = ""
        self.uploadArtefactImage.image = UIImage(named: "upload")
        self.artefactImageView.image = UIImage(named: "image")
    }
}

extension ContextSheetViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        print("did Finish Picking Media")
        if let image = info["UIImagePickerControllerOriginalImage"] as? UIImage{
            artefactImageView.image = image
//            selectedImage = image
//            uploadArtefactImage.image = image
        }
        dismiss(animated: true, completion: nil)
    }
}

SiteTableViewCell 的代码：

protocol SiteTableViewCellDelegate {
    func goToSheetVC(sheetId: String)

}

class SiteTableViewCell: UITableViewCell {


    @IBOutlet weak var profileImageView: UIImageView!
    @IBOutlet weak var siteSheetLabel: UILabel!
    @IBOutlet weak var nameLabel: UILabel!

    var delegate: SiteTableViewCellDelegate?

    var sheet: Sheet? {
        didSet {
            updateView()
        }
    }

    var user: User? {
        didSet {
            setupUserInfo()
        }
    }

    func updateView() {
        siteSheetLabel.text = sheet?.siteCodeTextView

    }


    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    func setupUserInfo() {
        nameLabel.text = user?.username
        if let photoUrlString = user?.profileImageUrl {
            let photoUrl = URL(string: photoUrlString)
            profileImageView.sd_setImage(with: photoUrl, placeholderImage: UIImage(named: "placeholderImg"))
        }
    }


    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(self.siteSheetLabel_TouchUpInside))
        siteSheetLabel.addGestureRecognizer(tapGesture)
        siteSheetLabel.isUserInteractionEnabled = true
    }

    @objc func siteSheetLabel_TouchUpInside() {

        print(sheet?.id)

        if let id = sheet?.id{
            delegate?.goToSheetVC(sheetId: id)
        }
    }
    override func prepareForReuse() {
        super.prepareForReuse()
        profileImageView.image = UIImage(named: "placeholderImg")
    }

}

标签： swiftxcodefirebasefirebase-realtime-database

Answer 1

根据您所展示的罪魁祸首postId，您正在使用它从 Firebase 获取数据，但您没有在任何地方显示它的值是什么。当用户点击图像时，postId不会转移到SiteViewController.

在SiteViewController删除!并替换为 中?，放置一个将 postID 作为参数的初始化程序。

var postId:String?

func initPost(forImage postId: String) {
    self.postId=postId
}

在之前的新闻提要 VC 里面segueor didSelectForRow(我不知道你用什么来转换，初始化SiteViewController，所以当它出现时它知道要为哪个 ID 检索数据。

需要提及的另一件事是您正在使用observe但没有删除观察者。

编辑：这个答案是基于我不知道你的 HomeVC 是什么样子的。

     if segue.identifier == "SiteSegue" {
        let siteVC = segue.destination as! SiteViewController
        let postId = sender as! String
        siteVC.postId = postId

    }