如何使用firebase从数据库中提取用户并在表视图中列出它们？

Question

我正在使用 firebase 制作 iOS 应用。我想检索数据库中的所有用户并在表格视图中显示他们的姓名和个人资料图片。这是我的TableViewCell 代码：

import UIKit
import FirebaseDatabase
import FirebaseAuth
import SDWebImage

class HomeTableViewCell: UITableViewCell {


    @IBOutlet weak var nameLabel: UILabel!
    @IBOutlet weak var profileImageView: UIImageView!
    @IBOutlet weak var likeImageView: UIImageView!
    @IBOutlet weak var messageImageView: UIImageView!
    @IBOutlet weak var likeCountButton: UIButton!

    var homeVC: HomeViewController?
    var postReference: DatabaseReference!

    var post: UserFile?{
        didSet {
            updateView()
        }
    }

    var user: UserFile? {
        didSet {
            updateUserInfo()
        }
    }

    override func awakeFromNib() {
        super.awakeFromNib()

        nameLabel.text = ""

        let berryTapGesture = UITapGestureRecognizer(target: self, action: #selector(handleLikeTap))

        likeImageView.addGestureRecognizer(berryTapGesture)
        likeImageView.isUserInteractionEnabled = true

    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)
    }

    func updateView() {
        if let photoURL = post?.picURL {
            profileImageView.sd_setImage(with: URL(string: photoURL))
        }

        API.Post.REF_POSTS.child(post!.id!).observeSingleEvent(of: .value, with: { postSnapshot in
            if let postDictionary = postSnapshot.value as? [String:Any] {
                let post = UserFile.transformPost(postDictionary: postDictionary, key: postSnapshot.key)
                self.updateLike(post: post)
            }
        })
        API.Post.REF_POSTS.child(post!.id!).observe(.childChanged, with: { snapshot in
            if let value = snapshot.value as? Int {
                self.likeCountButton.setTitle("\(value) berries", for: .normal)
            }
        })
    }

    func updateLike(post: UserFile) {
        let imageName = post.berries == nil || !post.isBerried! ? "berry" : "berrySelected"
        likeImageView.image = UIImage(named: imageName)

        // display a message for berries
        guard let count = post.berryCount else {
            return
        }

        if count != 0 {
            likeCountButton.setTitle("\(count) berries", for: .normal)
        } else if post.berryCount == 0 {
            likeCountButton.setTitle("Be the first to Like this", for: .normal)
        }
    }

    func incrementberries(forReference ref: DatabaseReference) {
        ref.runTransactionBlock({ (currentData: MutableData) -> TransactionResult in
            if var post = currentData.value as? [String : AnyObject], let uid = Auth.auth().currentUser?.uid {
                var berries: Dictionary<String, Bool>
                berries = post["berries"] as? [String : Bool] ?? [:]
                var likeCount = post["berryCount"] as? Int ?? 0
                if let _ = berries[uid] {
                    // Unlike the post and remove self from stars
                    likeCount -= 1
                    berries.removeValue(forKey: uid)
                } else {
                    // Like the post and add self to stars
                    likeCount += 1
                    berries[uid] = true
                }
                post["berryCount"] = likeCount as AnyObject?
                post["berries"] = berries as AnyObject?

                currentData.value = post

                return TransactionResult.success(withValue: currentData)
            }
            return TransactionResult.success(withValue: currentData)
        }) { (error, committed, snapshot) in
            if let error = error {
                print(error.localizedDescription)
            }

            if let postDictionary = snapshot?.value as? [String:Any] {
                let post = UserFile.transformPost(postDictionary: postDictionary, key: snapshot!.key)
                self.updateLike(post: post)
            }
        }
    }

    func handleLikeTap() {
        postReference = API.Post.REF_POSTS.child(post!.id!)
        incrementberries(forReference: postReference)
    }

    override func prepareForReuse() {
        super.prepareForReuse()
        profileImageView.image = UIImage(named: "industribune-default-no-profile-pic")
    }

    func updateUserInfo() {
        nameLabel.text = user?.username
        if let photoURL = user?.profileImageURL {
            profileImageView.sd_setImage(with: URL(string: photoURL), placeholderImage: UIImage(named: "industribune-default-no-profile-pic"))
        }
    }


}

我正在我的HomeViewController 上显示此单元格：

import UIKit
import FirebaseAuth
import FirebaseDatabase
import FirebaseStorage
import Firebase

class HomeViewController: UIViewController {


    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var activityIndicatorView: UIActivityIndicatorView!

    var posts = [UserFile]()
    var users = [UserFile]()

    override func viewDidLoad() {
        super.viewDidLoad()
        // for performance set an estimated row height
        tableView.estimatedRowHeight = 1
        // but also request to dynamically adjust to content using AutoLayout
        tableView.rowHeight = UITableViewAutomaticDimension

        //tableView.delegate = self
        tableView.dataSource = self

        loadPosts()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func loadPosts() {
        activityIndicatorView.startAnimating()

        API.User.observePosts { (newPost) in
            guard let userID = newPost.uid else { return }
            self.fetchUser(uid: userID, completed: {
                // append the new Post and Reload after the user
                // has been cached
                self.posts.append(newPost)
                self.activityIndicatorView.stopAnimating()
                self.tableView.reloadData()
            })
        }
    }

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

        API.User.observeUser(withID: uid) { user in
            self.users.append(user)

            completed()
        }
    }


}

extension HomeViewController: UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return posts.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "HomeTableViewCell", for: indexPath) as! HomeTableViewCell

        cell.post = posts[indexPath.row]
        cell.user = users[indexPath.row]
        cell.homeVC = self

        return cell
    }

}

我的项目中有很多疯狂的事情发生，所以如果您有任何问题，请告诉我以及我做错了什么。如果理解起来太复杂，我已经准备好删除所有内容并重新开始。

老实说，我确实认为我遵循了所有准则来提出问题，所以不喜欢关闭这个问题或其他什么。

Answer 1

这是很多代码。试试这个超级简化的例子。为此，用户节点仅将名称存储为子节点，但它也可以包含图像、电子邮件、地址等。

示例用户节点

users
  uid_0:
     name: "Bert"
  uid_1:
     name: "Ernie"

还有一些代码

var usersArray = [ [String: Any] ]()  //an array of dictionaries.

class ViewController: UIViewController {
    //set up firebase references here
   override func viewDidLoad() {
        super.viewDidLoad()

        let usersRef = self.ref.child("users")
        usersRef.observeSingleEvent(of: .value, with: { snapshot in
         for child in snapshot.children {
              let snap = child as! DataSnapshot
              let userDict = snap.value as! [String: Any]
              self.usersArray.append(userDict)
         }
         self.tableView.reloadData()
   })

和 tableView 委托方法

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return self.usersArray.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "HomeTableViewCell", for: indexPath) as! HomeTableViewCell

    let userDict = self.usersArray[indexPath.row]
    cell.text = userDict["name"] as! String
    //cell.imge = userDict["image"] etc etc

    return cell
}

现在……说了这么多。这是 UserClass 对象数组而不是字典的完美用途。

这是一个起点......

class UserClass {
   var name = ""
   var image = ""

   func init(snap: DataSnapshot) {
     //populate the vars from the snapshot
   }
}

var userClassArray = [UserClass]()

请勿复制粘贴，因为可能存在拼写错误，但它应该为您指明正确的方向。