swift - 从firebase中获取相对于用户uid的用户名以显示评论

Question

我正在创建保存评论的 Collection View ，我在其中从 Firebase 获取评论、评论 ID、帖子 ID 和用户 UID。当我尝试获取与用户 uid 相关的用户详细信息并附加注释时，它不起作用。我认为这是因为我将 snapshot.value 添加到用户引用中，因此它不再具有注释引用。如何获取评论和与 UID 相关的用户名并将其显示在评论 Collection View 中？

Firebase 中的层次结构如下所示: Click here.

在我的 View 帖子 Controller 中，我正在获取这样的评论。

  var comments = [Comment]()
fileprivate func fetchComments() {
    guard let postID = self.post?.id else {return}
    let commentRef = Database.database().reference().child("comments").child(postID)
    commentRef.observe(.childAdded, with: { (snapshot) in

        guard let dict = snapshot.value as? [String: Any] else {return}

        guard let uid = dict["uid"] as? String else {return}

        let userRef = Database.database().reference().child("users/\(uid)/profile")
        userRef.observe(.value, with: { snapshot in

            if (snapshot.value as? [String: Any]) != nil {
                //let snap = snapshot.value as? [String: Any]
                var comment = Comment(dictionary: dict)


                comment.user = snapshot.value as? User
                self.comments.append(comment)
                print(comment)
                self.commentCollectionView.reloadData()
                }
            })

        })
}

像这样设置评论的 Collection View 。

extension ViewPostViewController: UICollectionViewDelegate, UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return comments.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "commentCell", for: indexPath) as! CommentCollectionViewCell
    cell.comment = self.comments[indexPath.item]
    return cell
}
}

我的 CommentsCollectionViewCell.swift 有以下代码:

class CommentCollectionViewCell: UICollectionViewCell {
@IBOutlet weak var usernameLabel: UILabel!
@IBOutlet weak var commentLabel: UILabel!
@IBOutlet weak var timePostedLabel: UILabel!

var comment: Comment? {
    didSet {
        guard let comment = comment else {return}
        guard let username = comment.user?.username else {return}
        print(username)
        commentLabel.text = comment.comment
        usernameLabel.text = comment.user?.username
    }
}
}

评论模型类有以下代码:

struct Comment {

var user: User?

let comment: String

let uid: String

init(dictionary: [String: Any]) {
    self.comment = dictionary["comment"] as? String ?? ""
    self.uid = dictionary["uid"] as? String ?? ""
}
}

Answer 1

首先，我会重构您的代码，将用户名包含在评论存储桶中，以节省您在设备上的工作量，以便稍后从多个源中提取它。

这很容易解决。将一两行代码添加到您的 saveToFirebase 函数中，并将一两行代码添加到您的 fetchComments 函数中。

但是如果你想保持它的结构方式，我会这样做:

func getComments(_ post: String, completion:  @escaping (_ info: [String?], _ error: NSError?) -> Void)  { 
    Database.database().reference.child("comments").child(postID).observeSingleEvent(of: .value) { (snapshot) in
        if let snapshots = snapshot.children.allObjects as? [DataSnapshot] {
            for snap in snapshot {
                if let dict = snap.value as? Dictionary<String, AnyObject> {
                    completion([dict["comment"],dict["uid"]],nil) // send data through handler
                } else { completion([], someError) }
            }
        } else { completion([], someError) }
    }
}


func getUserName(_ uid: String, completion:  @escaping (_ info: [String: Any]?, _ error: NSError?) -> Void)  { 
    Database.database().reference.child("users").child(uid).observeSingleEvent(of: .value) { (snapshot) in
        completion([snapshot],nil) // send data back
    } 
}

然后，当您设置内容时，您可以在 collectionView 内部调用如下函数:

        // or wherever you get your postID's from
getComments(posts[indexPath.row], completion: { (info, err) in 
    if err != nil { 
        print(err!.localizedDescription) 
    } else { 
        // info is available find user
        guard let uid = info[1] as? String? else { return }
        // do whatever else you want to with the info here 
        // like populate cell data (perform on main thread)
        getUserName(uid, completion: { (snapDict, err) in
            if err != nil {
                // handle error
            } else {
                // get Username from dictionary and do what you want with it
        }) // end getUserName
    } 
}) // end getComments