swift - 循环遍历 Firebase 数据会生成空表？

Question

我正在尝试循环遍历我的 Firebase 数据库并将其全部放入一个数组中。然而，当我执行它时，数组总是空的。我该怎么做？谢谢。

categories = ["Appliances", "Arts & Crafts", "Beauty & Personal Care", "Books", "Clothing", "Electronics", "Home & Kitchen", "Movies & TV", "Sports & Outdoors", "Toys & Games", "Video Games", "Other"]

    for items in categories {

        let ref = FIRDatabase.database().reference(withPath: "items").child(items)

        ref.observe(.value, with: { (snapshot) in

            for items in snapshot.children {

                let item = Item(snapshot: items as! FIRDataSnapshot)
                self.allItems.append(item)

            }

            self.tableView.reloadData()

        })

    }

Answer 1

假设您的数据库已设置为此工作:

categories = ["Appliances", "Arts & Crafts", "Beauty & Personal Care", "Books", 

    "Clothing", "Electronics", "Home & Kitchen", "Movies & TV", "Sports & Outdoors", "Toys & Games", "Video Games", "Other"]

     for items in categories {

         let ref = FIRDatabase.database().reference(withPath: "items")

         ref.observe(.value, with: { (snapshot) in
             let value = snapshot.value as? NSDictionary{
                 for item in value.allKeys{
                     if let foundItem = value[item] as? String{
                         self.allItems.append(foundItem)
                     }
                 }
             }
             self.tableView.reloadData()
         })
    }

如果您单独声明 Firebase 引用，然后执行 ref.child("items).observe

，也可能对您有帮助