从Firebase获取数据 [英] Get data from Firebase

问题描述

我正在尝试从Firebase获取数据，我尝试过这样：

I am trying to get data from Firebase, I have tried like this:

FIREBASE_REF.childByAppendingPath("tasks").observeEventType(.Value, withBlock: { (snapshot) -> Void in
            print(snapshot.value)
            self.tasks = [Task]()
            var task = Task()
            let data = snapshot.value as! NSDictionary
            let tasksFromServer = data.allValues as! [NSDictionary]
            for taskFromServer in tasksFromServer {
                task.description = taskFromServer.objectForKey("description") as! String
                task.startTime = taskFromServer.objectForKey("startTime") as! String
                task.endTime = taskFromServer.objectForKey("endTime") as! String
                task.progress = taskFromServer.objectForKey("progress") as! Int
                let priorityTemp = taskFromServer.objectForKey("priority") as! Int
                switch priorityTemp {
                case 0: task.priority = .Low
                case 1: task.priority = .Medium
                case 2: task.priority = .High
                default: break
                }
                task.assignee = taskFromServer.objectForKey("assignee") as! String
                self.tasks.append(task)
            }
            MBProgressHUD.hideAllHUDsForView(self.view, animated: true)
            self.tableView.reloadData()
        }

但它在此行中显示错误：

but it shows error in this line:

let data = snapshot.value as! NSDictionary

它说：无法转换类型'__NSArrayM'的值（0x10ebfc8d8 ）到'NSDictionary'（0x10ebfcd60）。

来自Firebase的数据如下：

My data from Firebase like this:

但另一方面，我在另一个ViewController中使用另一个代码从Firebase获取用户名和角色，它有效。

But in other side, I use another code in another ViewController to get users name and role from Firebase, it works.

FIREBASE_REF.childByAppendingPath("users").observeEventType(.Value, withBlock: { (snapshot) -> Void in
            self.names = []
            self.roles = []
            let data = snapshot.value as! NSDictionary
            let employees = data.allValues as! [NSDictionary]
            for employee in employees {
                let name = (employee.objectForKey("firstName") as! String) + " " + (employee.objectForKey("lastName") as! String)
                self.names.append(name)
                let role = employee.objectForKey("position") as! String
                self.roles.append(role)
            }
            MBProgressHUD.hideAllHUDsForView(self.view, animated: true)
            self.collectionView.reloadData()
        }) 

但为什么第一个代码总是崩溃。

But why the first code always crash.

任何帮助都将受到赞赏。谢谢。

Any helps would be appreciated. Thanks.

推荐答案

如果超过50％的密钥介于0和最大密钥之间，Firebase会将字典对象转换为数组（确切地说）你的情况只有一个零元素。）

Firebase transforms your dictionary object to an array if more than 50% of keys are between 0 and maximum key (exactly your case with one zero element).

https://www.firebase.com/docs/ios/guide/understanding-data.html#section-arrays-in-firebase

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