如何通过swift ios中的键值读取子或过滤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项目和价格，我希望能够打印..

输出：

• Red Chair 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

由于您要为每个项目执行相同的代码，因此您需要使用.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中使用你的代码，看到有两个问题。所以三者合起来了：

1. 您正在侦听.Value事件，但您的区块一次只处理一个项目。解决方案：

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

2. 您正在收听顶层的.Value活动，但您要在users下添加这些项目。解决方案：

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

3. 您正在测试价格是否为Int，但是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]
   

通过这些更改，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