完成的 Firebase 嵌套查询

Question

我正在尝试使用 firebase 获取嵌套数据。但是我的代码有些问题。

我的 Firebase 数据是：

-contentlikes
    -userID: true,
    -userID: true,
    -userID: true
-users
    -userID
        -name: "John"

我的代码是：

override func viewWillAppear(_ animated: Bool) {
    self.displayUserKeys(completionHandler: { (userKeysInside, errorInside) in
        if userKeysInside != nil {
            self.userKeys = userKeysInside!
            print(self.userKeys)
        }
        self.detailUserTableView.rowHeight = UITableViewAutomaticDimension
        self.detailUserTableView.estimatedRowHeight = 64
        self.detailUserTableView.dataSource = self
        self.detailUserTableView.delegate = self
        self.detailUserTableView.reloadData()
    })
}

func displayUserKeys(completionHandler: @escaping ([String]?, Error?) -> ()) {
    self.detailUserHandler = DataService.dataService.CONTENTLIKE_REF.observe(.value, with: { (snapshot) in
        self.userKeys.removeAll()
        var userKeyInside = [String]()
        for child in snapshot.children.allObjects as! [FIRDataSnapshot] {
            let key = child.key
            userKeyInside.append(key)
        }
        completionHandler(userKeyInside, nil)
    }) { (errorInside) in
        completionHandler(nil, errorInside)
    }
}

我想获得用户，但不知道该怎么做。

Answer 1

您需要根据从第一个查询中获得的键从另一个用户节点获取用户详细信息。 Firebase 不提供连接查询，因此我们必须再次查询类型为 ObserveSingleEvent 的用户详细信息。

这是一个示例代码。我是在没有 xcode 编辑器的情况下编写的，所以请原谅任何愚蠢的错误。

        func displayUserKeys(completionHandler: @escaping ([String]?, Error?) -> ()) {
            self.detailUserHandler = DataService.dataService.CONTENTLIKE_REF.observe(.value, with: { (snapshot) in
                self.userKeys.removeAll()
                var userKeyInside = [String]()
                var userFetched = 0

                for child in snapshot.children.allObjects as! [FIRDataSnapshot] {
                    let key = child.key

                    //Query again to fetch user details.   
                    DataService.dataService.USER_REF.path(key).observeSingleEvent(.value, with: { (snapshot) in
                                userFetched = userFetched + 1
                                let user = snapshot.value  
                               //Append user to the array
                               userInside.append(user)
                      //Return back the array when all the user details as fetched.
                      if(userFetched == snapshot.children.count){
                          completionHandler(userInside, nil)
                       }
                    })
                }



            }) { (errorInside) in
                completionHandler(nil, errorInside)
            }
        }