ios - 在 Firebase (Swift) 中获取所有用户的同一个 child

Question

我目前正在 Firebase 中构建一个应用程序，我希望获得所有用户菠萝率。

这是树:

user1: uid1 {
  fruits: {
    apple: 3
    pineapple: 5
  }
}

user2: uid2 {
  fruits: {
    apple: 4
    pineapple: 2
  }
}

我试过这段代码:

var ref = FIRDatabase.database().reference()
ref.queryOrderedByChild("fruits")
            .observeSingleEventOfType(.Value, withBlock: { (snapshot) in
                if ( snapshot.value is NSNull ) {
                    print("not found")
                } else {
                    for child in snapshot.children {
                        let rate = child.value["pineapple"] as! String
                        print(rate)
                    }
                }
            })

但它给我一个解包 Nil 的错误。

结构图:

Answer 1

应该是这样的

  var ref = FIRDatabase.database().reference()
     ref.queryOrderedByChild("user2")
        .observeSingleEventOfType(.Value, withBlock: { (snapshot) in
            if snapshot.exists() {
                for child in (snapshot.value?.allValues)! {
                    if let fruits = child["Fruits"] as? [String:String]{
                        let rate = fruits["pineapple"]
                        print(rate)
                    }
                }
            }
        })