swift - 无法从 Firebase 获取值(value)

Question

我试图在我设置的 Firebase 数据库中获取一个值，但我在尝试获取它时遇到了问题。在我的程序中有一个部分，我遍历 Cities 下的每个 child 并获取每个城市的名称。我认为尝试获取同一部分中每个城市的状态是个好主意，但我无法获取。下面是 JSON 对象的示例。我觉得我很接近但缺少将它们放在一起的东西。

"Users" : {
    "NPNBig20BXNpX4Rz0UbMyiKAarY2" : {
      "Cities" : {
        "New York City" : {
          "Status" : "Empty"
        },
        "Atlanta" : {
          "Status" : "Empty"
        },
        "Test City" : {
          "Status" : "Wow",
          "Value" : "Test"
        }
      },
      "Email" : "fakeemail@gmail.com"
    }
  }

代码:

guard let uid = userID else { return }
    let databaseRef = Database.database().reference(fromURL: "https://testApp.firebaseio.com/").child("Users").child(uid).child("Cities")
    var dataTest : [String] = []
    //var cityDictionary: [String:String]()
    databaseRef.observeSingleEvent(of: .value, with: {(snapshot) in
        for child in snapshot.children {
            let snap = child as! DataSnapshot
            let key = snap.key
            guard let value = snap.value else { return }
            //let testData = value["Status"] **Type Any has no subscript
            print("Key: ", key, "\nValue: ", value)
            dataTest.append(key)
        }
        completion(dataTest)
    })

这是打印输出

Key:  New York City 
Value:  {
    Status = Empty;
}
Key:  Sintra 
Value:  {
    Status = Empty;
}
Key:  Test City 
Value:  {
    Status = Wow;
    Value = Test;
}

Answer 1

以下是您可以从值获取Status的方法:

if let value = snap.value as? [String: AnyObject] {
    let Status = value["Status"] as? String ?? ""
}

你的完整代码将是:

guard let uid = userID else { return }
    let databaseRef = Database.database().reference(fromURL: "https://testApp.firebaseio.com/").child("Users").child(uid).child("Cities")
    var dataTest : [String] = []
    //var cityDictionary: [String:String]()
    databaseRef.observeSingleEvent(of: .value, with: {(snapshot) in
        for child in snapshot.children {
            let snap = child as! DataSnapshot
            let key = snap.key
            guard let value = snap.value else { return }
            //let testData = value["Status"] **Type Any has no subscript
            if let value = snap.value as? [String: AnyObject] {
                let Status = value["Status"] as? String ?? ""
            }
            print("Key: ", key, "\nValue: ", value)
            dataTest.append(key)
        }
        completion(dataTest)
    })