swift - 使用 Swift 3.0 从随机子路径从 Firebase 检索数据

Question

我正在尝试使用现有的字符串数组作为引用，从具有随机文件夹的目录中检索项目数组

我的数据是这样的:

 Items
  - RandomID
    -title : "text"
    -subtitle: "text"

到目前为止，这是我尝试过的方法，但它不起作用:

var array = [String]() //array to use as reference
var returnedItems = [Item]() //array of item objects

func retrieveData()
 {
     for i in array
      {
        let ref = main.child("Items")
        let query = ref.queryEqual(toValue: i)
        query.observeSingleEvent(of: .value, with: { (snapshot) in

            let item = Item!

            if snapshot.hasChild("title")
             {
               item.title = (snapshot.value as! NSDictionary)["title"] as? String
             }
            if snapshot.hasChild("subtitle")
             {
               item.subtitle = (snapshot.value as! NSDictionary)["subtitle"] as? String
             }

            returnedItems.append(item)
            self.tableView.reloadData()
            print("Item: \(self.returnedItems.map { $0.title})")

         })
     }
 }

任何帮助将不胜感激!提前致谢;)

Answer 1

如果你想检索所有的 child ，你可以只使用一个监听器(模仿 this example in the documentation ):

var array = [String]() //array to use as reference
var returnedItems = [Item]() //array of item objects

func retrieveData() {
    query.observeSingleEvent(of: .value, with: { (snapshot) in
        for child in snapshot.children {
            let item = Item!
            if child.hasChild("title") {
                item.title = (snapshot.value as! NSDictionary)["title"] as? String
            }
            if child.hasChild("subtitle") {
                item.subtitle = (snapshot.value as! NSDictionary)["subtitle"] as? String
            }

            returnedItems.append(item)
            self.tableView.reloadData()
            print("Item: \(self.returnedItems.map { $0.title})")
        })
    }
    // returnedItems will still be empty here, since the data hasn't
    // been loaded yet. See the note after this code snippet.
}

但请注意，此处读取数据仍将异步发生，因此当 retrieveData 返回时，returnedItems 仍为空。