从Firebase的数据库下载帖子时出错（Swift 3）

Question

我有一个社交应用，其中包含类似Facebook的帖子，但是当我尝试下载帖子时，它返回nil。

FIRDatabase.database().reference().child("following").child(FIRAuth.auth()!.currentUser!.uid).queryOrderedByValue().queryEqual(toValue: true).observeSingleEvent(of: .value, with: {(snap) in
    if let snapDict = snap.value as? [String:AnyObject]{
        for each in snapDict{


            FIRDatabase.database().reference().child("Posts").child(String(each.key)).queryOrdered(byChild: "timestamp").observeSingleEvent(of: .value, with: {(snapshot) in

                if (snapshot.value != nil)
                {
                    self.Posts.append(snapshot.value as! NSDictionary)


                }

            }){(error) in

                print(error.localizedDescription)
            }

        }

    }

    self.homeTableView.reloadData()

    self.aivLoading.stopAnimating()
})

经过一些调试后，我将问题减少到此代码行，然后返回nil值

FIRDatabase.database().reference().child("Posts").child(String(each.key)).queryOrdered(byChild: "timestamp").observeSingleEvent(of: .value, with: {(snapshot) in

我代码的另一部分确实返回了您关注的人的列表，并以为是循环。

这是我的数据库的结构。

{
  "Posts" : {
    "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : {
      "-KbHUnL-RveUQa3MPSWp" : {
        "latitud" : "21.111401000574",
        "longitud" : "-89.6112191677094",
        "text" : "Fiesta en la Anahuac!!! ",
        "timestamp" : "1485295269.30773",
        "ubicacionN" : "Universidad Anáhuac Mayab"
      },
      "-KbI1azr6uFel-5uTZOD" : {
        "latitud" : "Optional(21.018988764483463)",
        "longitud" : "Optional(-89.614319546492695)",
        "text" : "Hola chicos",
        "timestamp" : "1485304393.77929",
        "ubicacionN" : "Calle 53-A 341"
      },
      "-KbNQWxjQhc0Ce_ZQbq9" : {
        "latitud" : "Optional(21.019219877217914)",
        "longitud" : "Optional(-89.614173537203683)",
        "text" : "Hola",
        "timestamp" : "1485394812.83039",
        "ubicacionN" : "Calle 53 341"
      }
    },
    "mt0fzirhMhazIcy90MRWuRpTfmE2" : {
      "-KbQOWfUnzY1JiS61J6-" : {
        "latitud" : "Optional(21.111502615883129)",
        "longitud" : "Optional(-89.611767497121221)",
        "text" : "Hola chicos!",
        "timestamp" : "1485444619.10931",
        "ubicacionN" : "Carretera Mérida-Progreso 96"
      }
    }
  },
  "follower" : {
    "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : {
      "mt0fzirhMhazIcy90MRWuRpTfmE2" : true
    },
    "mt0fzirhMhazIcy90MRWuRpTfmE2" : {
      "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : true
    }
  },
  "following" : {
    "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : {
      "mt0fzirhMhazIcy90MRWuRpTfmE2" : true
    },
    "mt0fzirhMhazIcy90MRWuRpTfmE2" : {
      "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : true
    }
  },
  "handles" : {
    "jcadmin" : "mt0fzirhMhazIcy90MRWuRpTfmE2",
    "jcbest" : "dEXaVLDOSPfJa3zTyUNqAEtVuMR2"
  },
  "user_profiles" : {
    "dEXaVLDOSPfJa3zTyUNqAEtVuMR2" : {
      "about" : "Hola Mundo",
      "handle" : "jcbest",
      "name" : "Juan Carlos Estevez Rodriguez",
      "profile_pic" : "https://firebasestorage.googleapis.com/v0/b/jalo-267da.appspot.com/o/user_profiles%2FOptional(%22dEXaVLDOSPfJa3zTyUNqAEtVuMR2%22)%2Fprofile_pic?alt=media&token=bfc3c516-7849-472c-b7cd-9668965a5dbe"
    },
    "mt0fzirhMhazIcy90MRWuRpTfmE2" : {
      "about" : "Hola chicos",
      "handle" : "jcadmin",
      "name" : "Juan Carlos",
      "profile_pic" : "https://firebasestorage.googleapis.com/v0/b/jalo-267da.appspot.com/o/user_profiles%2FOptional(%22mt0fzirhMhazIcy90MRWuRpTfmE2%22)%2Fprofile_pic?alt=media&token=b741b6c1-0bc5-446d-a1e5-159b21e770d2"
    }
  }
}

这是我的全部代码。 https://www.dropbox.com/sh/u7saz4mdbehw1gd/AACv2rZH7M8jS_lU-plSqwc5a?dl=0

Answer 1

如果这是有效的数据集，则说明您在查询中查找错误的内容，但可能是我不理解您的数据！

我假设currentUser是dEXaVLDOSPfJa3zTyUNqAEtVuMR2 ，并且第一个获得以下查询的查询应返回mt0fzirhMhazIcy90MRWuRpTfmE2

您在帖子中没有任何关于mt0fzirhMhazIcy90MRWuRpTfmE2引用，因此您永远都不会在第二个查询中得到任何返回的信息...

Answer 2

经过大量调试后，我发现了问题所在，因为它解决了这个问题

 FIRDatabase.database().reference().child("Posts").child(String(each.key)).queryOrdered(byChild: "timestamp").observeSingleEvent(of: .value, with: {(snapshot) in

                if (snapshot.value != nil)
                {
                    self.Posts.append(snapshot.value as! NSDictionary)


                }

            }){(error) in

                print(error.localizedDescription)
            }

该查询实际上正在下载所有帖子，但是它们被保存在一个非静态变量中（noob错误），所以我要做的唯一一件事就是在收到每个帖子之后重新加载数据，也就是说，它需要像这个：

FIRDatabase.database().reference().child("Jalas").child(each.key).queryOrderedByKey().observe(.childAdded, with: { (snapshot:FIRDataSnapshot) in

                        print(snapshot.value as! NSDictionary)

                        self.Jalas.append(snapshot.value as! NSDictionary)
                        self.homeTableView.reloadData()
                    })

因此完整的代码如下所示：

        self.homeTableView.delegate = self
        self.homeTableView.dataSource = self

        self.loggedInUser = FIRAuth.auth()?.currentUser

        print("LoggedInUser: " + (self.loggedInUser?.uid)!)


        FIRDatabase.database().reference().child("following").child(FIRAuth.auth()!.currentUser!.uid).queryOrderedByValue().queryEqual(toValue: true).observeSingleEvent(of: .value, with: {(snap) in

            //if let snapDict = snap.value as? [String:AnyObject]{

            let sanpDict = snap.value as? [String:AnyObject]
            if (sanpDict != nil)
            {
                for each in sanpDict!{

                    print("each.key es: " + String(each.key))

                    FIRDatabase.database().reference().child("Jalas").child(each.key).queryOrderedByKey().observe(.childAdded, with: { (snapshot:FIRDataSnapshot) in

                        print(snapshot.value as! NSDictionary)

                        self.Jalas.append(snapshot.value as! NSDictionary)
                        self.homeTableView.reloadData()
                    })

                }
        }


            self.aivLoading.stopAnimating()
        })