不能在火力地堡

Question

得到节点的值我读了很多例子，他们大多有旧式（即使它们被写入当年）。请帮忙了解我的代码错在哪里？它是建立，但我不能让一个价值123456

import UIKit 
import Firebase 

class ViewController: UIViewController { 
    @IBOutlet weak var val_txt: UITextField! 
    let ref = FIRDatabase.database().reference() 
    var barcode = 0 

    override func viewDidLoad() { 
    super.viewDidLoad() 
    FIRAuth.auth()?.signIn(withEmail: "*****@gmail.com", password: "*****", completion: {(user,error) in print("Авторизация Ок!!!")}) 

    } 
    @IBAction func getData_btn(_ sender: Any) { 
    ref.child("goods").child("1").observe(FIRDataEventType.value, with: {(snapshot) in 
    let postDict = snapshot.value as? [String:AnyObject] ?? [:] 
    print(postDict["barcode"] as? Int) 
    }) 
    print(barcode) 
} 

我已经改变的代码，以便了解是否打印执行，我发现它不

print("Method started") 
ref.child("goods").child("1").observe(FIRDataEventType.value, with:{(snapshot) in 
    let postDict = snapshot.value as? [String:AnyObject] ?? [:] 
    print("Method is executing") 
    }) 
    print("Method completed") 

我也得到打印

"Method started" 
"Method completed" 

Answer 1

如果你想只为 “1” 值：

var ref: FIRDatabaseReference! 
ref = FIRDatabase.database().reference() 
ref.child("goods").child("1").observeSingleEvent(of: .value, with: { (snapshot) in 
      let id = snapshot.childSnapshot(forPath: "barcode") 
      print(id) 
     }) 

，但如果你希望所有条形码：

var ref: FIRDatabaseReference! 
    ref = FIRDatabase.database().reference() 
    ref.child("goods").observeSingleEvent(of: .value, with: { (snapshot) in 
     if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] { 

      for snap in snapshots 
      { 
       let barcode = snap.childSnapshot(forPath: "barcode").value! as! String 
       print(barcode) 
      } 
     } 
    }) 

Answer 2

的只是两行代码let ref = FIRDatabase.database().reference()没有指向引用URL，因为在初始化过程中你的火力点不在你的应用程序委托文件中配置（不叫FIRApp.configure()）。

所以放在func viewDidLoad()如下：

import UIKit 
import Firebase 

class ViewController: UIViewController { 
    @IBOutlet weak var val_txt: UITextField! 
    let ref:FIRDatabaseReference! 
    var barcode = 0 

    override func viewDidLoad() { 
    super.viewDidLoad() 
    ref:FIRDatabaseReference = FIRDatabase.database().reference() 
    FIRAuth.auth()?.signIn(withEmail: "*****@gmail.com", password: "*****", completion: {(user,error) in print("Авторизация Ок!!!")}) 

    }