如何通过 swift ios 中的键值读取子数据或过滤 firebase 数据

Question

我是 swift 和 firebase 的新手，我正在尝试使用下面的代码打印所有商品和价格，我希望能够打印 ..

输出：

红椅100
沙发床120

  var ref =  Firebase(url: "https://jeanniefirstapp.firebaseio.com")

var item1     =  ["name": "Alan Turning", "item" : "Red Chair", "price": "100"]
var item2     =  ["name": "Grace Hopper", "item": "Sofa Bed"  , "price": "120"]
var item3     =  ["name": "James Cook"  , "item": "White Desk", "price": "250"]
var item4     =  ["name": "James Cook"  , "item": "Mattress Cal King", "price": "100"]

override func viewDidLoad() {
    super.viewDidLoad()
    var usersRef = ref.childByAppendingPath("users")

    var users = ["item1": item1, "item2": item2, "item3" : item3 , "item4" : item4 ]

    usersRef.setValue(users)


}
ref.queryOrderedByChild("price").observeEventType(.Value, withBlock: { snapshot in
    if let price = snapshot.value["price"] as? Int {
        println("\(snapshot.key) price at \(price) Dollars ")
        println(snapshot.key)
    }
})

Answer 1

因为你想为每个项目执行相同的代码，你会想使用 .ChildAdded:

ref.queryOrderedByChild("price").observeEventType(.ChildAdded, withBlock: { snapshot in
  if let price = snapshot.value["price"] as? Int {
    println("\(snapshot.key) price at \(price) Dollars ")
    println(snapshot.key)
  }
})

有关更多信息和示例，请参阅 page on retrieving data in the Firebase guide for iOS developers。

更新

我最终在本地 xcode 中使用了您的代码，发现有两个问题。所以这三个加起来：

您正在侦听 .Value 事件，但您的块一次处理一个项目。解决方案：

ref.queryOrderedByChild("price")
   .observeEventType(.ChildAdded, withBlock: { snapshot in

您正在监听顶级的 .Value 事件，但您正在添加 users 下的项目。解决方案：

ref.childByAppendingPath("users")
   .queryOrderedByChild("price")
   .observeEventType(.ChildAdded, withBlock: { snapshot in

您正在测试价格是否为 Int，但将它们添加为字符串。解决方案：

var item1     =  ["name": "Alan Turning", "item" : "Red Chair", "price": 100]
var item2     =  ["name": "Grace Hopper", "item": "Sofa Bed"  , "price": 120]
var item3     =  ["name": "James Cook"  , "item": "White Desk", "price": 250]
var item4     =  ["name": "James Cook"  , "item": "Mattress Cal King", "price": 100]

进行这些更改后，代码会为我打印出这些结果：

item1 price at 100 Dollars 
item1
item4 price at 100 Dollars 
item4
item2 price at 120 Dollars 
item2
item3 price at 250 Dollars 
item3

如何通过 swift ios 中的键值读取子数据或过滤 firebase 数据

How to read child or filter firebase data by its key value in swift ios

ios

firebase

swift

更新