Tableview 中的 Swift Firebase Firestore 数据

Question

我无法让我的 tableView 加载来自 Firebase Firestore 的数据。我在 generateMore() 函数中遍历 cmets 文档，并将添加注释作为 AttributedTextComment 分配给数组。但是当我在视图控制器的viewDidLoad() 中设置数组时，数组保持为空，我不知道为什么。谢谢你的帮助！此外，我正在使用可以在 Github 上找到的 SwiftyComments 库，如果这有助于理解代码。

编辑：generateMore() 函数中的数组按预期填充了所有 Firestore 数据，但由于某种原因，ViewController 中的allcomments 永远不会设置为等于该数组。

class RandomDiscussion {
    var comments: [AttributedTextComment]! = []
    var colRef: CollectionReference!

func generateMore() -> [AttributedTextComment] {
    var arr: [AttributedTextComment]! = []
    colRef = Firestore.firestore().collection("pictures/TKIiXdontufmDM1idbVH/comments")
    let query = colRef.whereField("body", isGreaterThan: "")
    query.getDocuments() { (querySnapshot, err) in
        if err != nil {
            print("error")
            return
        }
        else {
            for doc in querySnapshot!.documents {
                print("\(doc.documentID) => \(doc.data())")
                let com = AttributedTextComment()
                com.posterName = doc.get("username") as? String
                com.body = doc.get("body") as? String
                com.upvotes = doc.get("upvotes") as? Int
                com.downvotes = doc.get("downvotes") as? Int
                arr.append(com)
                NotificationCenter.default.post(name: NSNotification.Name(rawValue: "load"), object: nil)
            }
        }
    }
    return arr
}
}


class RedditCommentsViewController: CommentsViewController {

    private let commentCellId = "redditComentCellId"
    var allComments: [AttributedTextComment] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(RedditCommentCell.self, forCellReuseIdentifier: commentCellId)

        tableView.backgroundColor = RedditConstants.backgroundColor

        NotificationCenter.default.addObserver(self, selector: #selector(loadList), name: NSNotification.Name(rawValue: "load"), object: nil)

        allComments = RandomDiscussion().generateMore()
        currentlyDisplayed = allComments


        self.swipeToHide = true
        self.swipeActionAppearance.swipeActionColor = RedditConstants.flashyColor

    }

    override open func commentsView(_ tableView: UITableView, commentCellForModel commentModel: AbstractComment, atIndexPath indexPath: IndexPath) -> CommentCell {
        let commentCell = tableView.dequeueReusableCell(withIdentifier: commentCellId, for: indexPath) as! RedditCommentCell
        let comment = currentlyDisplayed[indexPath.row] as! RichComment
        commentCell.level = comment.level
        commentCell.commentContent = comment.body
        commentCell.posterName = comment.posterName
        //commentCell.date = comment.soMuchTimeAgo()
        commentCell.upvotes = comment.upvotes
        commentCell.isFolded = comment.isFolded && !isCellExpanded(indexPath: indexPath)
        return commentCell
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.navigationController?.navigationBar.barTintColor = RedditConstants.flashyColor
        self.navigationController?.navigationBar.tintColor = .white
        UIApplication.shared.statusBarStyle = .lightContent
    }
    @objc func loadList(){
        self.tableView.reloadData()
    }
}

Answer 1

如果 Firebase 查询没有任何问题，您的功能可能会失败。

将 completionHandler 与 for 语句和 Firebase 查询结合使用可以让事情变得非常简单。

将您的 generateMore 函数转换为：

func generateMore(completionHandler: @escaping (Bool, [AttributedTextComment]) -> Void) {
    var arr: [AttributedTextComment]! = []
    colRef = Firestore.firestore().collection("pictures/TKIiXdontufmDM1idbVH/comments")
    let query = colRef.whereField("body", isGreaterThan: "")
    query.getDocuments() { (querySnapshot, err) in
        if err != nil {
            print("error")
            completionHandler(false, [])
        }
        else {
            for doc in querySnapshot!.documents {
                print("\(doc.documentID) => \(doc.data())")
                let com = AttributedTextComment()
                com.posterName = doc.get("username") as? String
                com.body = doc.get("body") as? String
                com.upvotes = doc.get("upvotes") as? Int
                com.downvotes = doc.get("downvotes") as? Int
                arr.append(com)
            }

            completionHandler(true, arr)
        }
    }

}

用法：

override func viewDidLoad() {
        super.viewDidLoad()
        // ...
        allComments = RandomDiscussion().generateMore { (success, comments) in

        if success { 

        currentlyDisplayed = comments
        self.tableView.reloadData()
        // OR
        NotificationCenter.default.post(name: NSNotification.Name(rawValue: "load"), object: nil)
        }
     }

        //...

    }