Question

我目前正在构建一个应用程序，其中有一个主要供稿，该供稿显示了您关注的所有人的帖子。当您关注某人时，他们的所有帖子都会添加到您的“供稿”中。在我的Firebase数据库中，有一个供稿节点，其中包含对您关注的每个人的帖子的引用，包括当前用户自己创建的帖子。我有一个函数“ loadPosts（）”，该函数获取对每个用户帖子的引用，获取帖子的数据，然后将该数据添加到数组中，然后显示在collectionView中。

我正在尝试使用基于“ creationDate”的查询从firebase对该数据进行分页，并且当我不关注任何人时，我的代码可以正常工作，但是一旦我关注具有不同userId的人，主供稿就开始复制帖子而不正确地订购它们。这是我正在获取的数据的快照：

简单来说，数据结构为：

Sub company_statement()
    Dim lr As Long
    Dim ws As Worksheet
    Dim vcol, i As Integer
    Dim icol As Long
    Dim myarr As Variant
    Dim title As String
    Dim titlerow As Integer 

    vcol = 6
    Set ws = Sheets("Company Statement Hanley")
    lr = ws.Cells(ws.Rows.Count, vcol).End(xlUp).Row
    title = "A1:AE1"
    titlerow = ws.Range(title).Cells(1).Row
    icol = ws.Columns.Count
    ws.Cells(1, icol) = "Unique" 

    For i = 2 To lr
        On Error Resume Next
        If ws.Cells(i, vcol) <> "" And _
            Application.WorksheetFunction.Match(ws.Cells(i, vcol), ws.Columns(icol), 0) = 0 Then 

            ws.Cells(ws.Rows.Count, icol).End(xlUp).Offset(1) = ws.Cells(i, vcol)
        End If
    Next 

    myarr = Application.WorksheetFunction.Transpose(ws.Columns(icol).SpecialCells(xlCellTypeConstants)) 

    ws.Columns(icol).Clear 

    For i = 2 To UBound(myarr)
        ws.Range(title).AutoFilter field:=vcol, Criteria1:=myarr(i) & ""
        If Not Evaluate("=ISREF('" & myarr(i) & "'!A1)") Then 

            Sheets.Add(after:=Worksheets(Worksheets.Count)).Name = myarr(i) & ""
        Else
            Sheets(myarr(i) & "").Move after:=Worksheets(Worksheets.Count)
        End If 

        ws.Range("A" & titlerow & ":A" & lr).EntireRow.Copy Sheets(myarr(i) & "").Range("A1") 

        Sheets(myarr(i) & "").Columns.AutoFit
    Next 

    ws.AutoFilterMode = False
    ws.Activate
End Sub

“ post_uid”属性是创建帖子的用户的uid，而“ creationDate”属性是创建帖子的时间。下面是loadPosts（）函数：

  "feed": {
            "uid": {
                "post1Key": {
                    "creationDate",
                    "post_uid"
                },
                "post2Key": {
                    "creationDate",
                    "post_uid"
                },
            }
        }

然后有一个名为show（forKey，uid）的函数，该函数从在loadPosts（）中获取的引用返回Post对象：

 static func loadPosts(posts: [Postt], isFinishedPaging: Bool, completion: @escaping ([Postt], Bool) -> Void) {
    guard let uid = Auth.auth().currentUser?.uid else {return}
    var pagingTemp = isFinishedPaging
    let ref = Database.database().reference().child("feed").child(uid)
    var query = ref.queryLimited(toLast: 4).queryOrdered(byChild: "creationDate")
    if posts.count > 0 {
        let value = posts.last?.creationDate.timeIntervalSince1970
        query = query.queryEnding(atValue: value)
    }
    query.observeSingleEvent(of: .value, with: { (snapshot) in
        var completedPosts = [Postt]()
        guard var allObjects = snapshot.children.allObjects as? [DataSnapshot] else {return}

        allObjects.reverse()
        if allObjects.count == 0 || allObjects.count == 1 {
            pagingTemp = true
        }
        if  posts.count > 0 && allObjects.count > 0 {
            allObjects.removeFirst()
        }
        let dispatchGroup = DispatchGroup()

        for postData in allObjects {
            guard let postDict = postData.value as? [String : Any],
                let postId = postDict["post_uid"] as? String
                else { return }
            dispatchGroup.enter()

            PostClient.show(forKey: postData.key, uid: postId) { (post) in
                if let post = post {
                    completedPosts.append(post)
                }
                dispatchGroup.leave()
            }
        }
        dispatchGroup.notify(queue: .main, execute: {
            completion(completedPosts, pagingTemp)
        })
    }) { (err) in
        print("Failed to fetch posts: ", err)
    }
}

问题不根源于show（）函数，仅仅是因为帖子没有按正确的顺序返回。

然后在collectionView的viewDidLoad方法中调用此loadPosts（）函数：

   static func show(forKey postKey: String, uid: String, completion: @escaping (Postt?) -> Void) {
    let ref = Database.database().reference().child("posts").child(uid).child(postKey)
    var images = [String]()
    Database.fetchUserWithUID(uid: uid) { (user) in
    ref.observeSingleEvent(of: .value, with: { (snapshot) in
        guard let post = Postt(snapshot: snapshot) else {
            return completion(nil)
        }
        let imageRef = ref.child("images")
        imageRef.observeSingleEvent(of: .value, with: { (imageSnapshot) in
        guard let values = imageSnapshot.value as? [String] else {return}
        values.forEach({ (value) in
            images.append(value)
        })
        post.imageUrls = images
        post.user = user
        completion(post)
        })
    })
   }
 }

从其他用户获取帖子时，Firebase分页不起作用

0 个答案: