Swift:从 Firebase 检索数据并在表格视图中显示
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【中文标题】Swift:从 Firebase 检索数据并在表格视图中显示【英文标题】:Swift: Retrieve data from Firebase and display in table view 【发布时间】:2018-06-27 09:15:24 【问题描述】:我正在制作一个包含图像新闻提要的应用程序 (HomeViewController)。用户可以点击与 SiteViewController 连接的每个图像,该图像具有空数据的表格视图和一个按钮,当单击该按钮时,用户可以上传数据到 ContextSheetViewController他们在新闻提要中单击的图像。用户然后按下上传,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,会出现错误:Unexpectedly found nil while unwrapping an Optional value。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 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")
【问题讨论】:
打印时是否看到来自 firebase 的数据? 【参考方案1】:根据您所显示的罪魁祸首是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
中删除!
并将其替换为?
,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segue
或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
,但您并没有移除观察者。
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
【讨论】:
感谢您的帮助!我对 swift 比较陌生,所以我不确定如何放置一个将 postID 作为参数的初始化程序。我已经编辑了我的问题并添加到我以前的 VC(新闻提要)中,以在 segue 中显示我的代码,因为它正在从那里检索 post.id 好的,我编辑了我的问题,向您展示如何在您的 VC 中放置初始化程序。但是在看到您的编辑后,您可以使用另一种方法,除非您没有将新闻提要 VC 设置为 SiteViewController 的委托。 我已经编辑了我的帖子,但这里最大的问题是你为什么使用 segue 而不是didSelectRowAt
??
我已经包含了我丢失的代码行,但是出现错误:“'SiteViewController' 类型的值没有成员'delegate',出现?
删除该行,现在它应该可以工作了,因为我已经在我的终端测试了它,但实现其他所有内容并让我知道..以上是关于Swift:从 Firebase 检索数据并在表格视图中显示的主要内容,如果未能解决你的问题,请参考以下文章
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