如何正確讀取viewDidLoad（）func上的Firebase數據庫？

Question

//Just a struct to save information about the User 
var user = AppUser() 

override func viewDidLoad() { 
    super.viewDidLoad() 

//Verify if user is logged in 
    verifyUser() 
    user.email = "blabla" 

    print("viewdidload user: \(user)") 

} 

override func viewDidAppear(_ animated: Bool) { 
    super.viewDidAppear(true) 

    print("viewdidappear user: \(user)") 

} 

func verifyUser() { 

    print("verify user called") 

    //Log in verification 
    guard let userID = Auth.auth().currentUser?.uid else { 
     perform(#selector(handleLogOut), with: nil, afterDelay: 0) 

     print("nil user") 

     return 
    } 

    ref.child("users").child(userID).observeSingleEvent(of: .value, with: { (snapshot) in 
     if let dictionary = snapshot.value as? [String: AnyObject] { 
      self.user = AppUser(dictionary: dictionary) 

      print(self.user) 
     } 
    }) { (error) in 
     print(error.localizedDescription) 
    } 
} 

控制檯：

verify user called 


viewdidload user: AppUser(id: nil, name: nil, email: 
Optional("blabla"), completedRegister: nil, FULLUser: nil) 


viewdidappear user: AppUser(id: nil, name: nil, email:     
Optional("blabla"), completedRegister: nil, FULLUser: nil) 


AppUser(id: nil, name: nil, email: Optional("x@gmail.com"),  
completedRegister: Optional(false), FULLUser: Optional(false)) 

的問題很簡單。有人可以解釋在「驗證用戶名」和「用戶」之間打印"print("viewDidLoad user:....")"與數據庫信息的可能性嗎？

問題是，當我嘗試獲取viewDidLoad上的用戶信息由於某種原因，該函數沒有獲取信息，所以值仍然爲零。這是時間問題嗎？

我試圖把一個循環功能verifyUser（）之後，但它從來沒有得到

out: 

    while user.email == nil { 
      print("Waiting...") 
     } 

所以......這就是問題

謝謝！

編輯阿納斯·門哈爾 這是我的結構。爲什麼做一個NSObject會更好？ 我做了一個結構，因爲我可以做兩inits不同（一個空）和NSObject的沒讓我出於某種原因

struct AppUser { 
var id: String? 
var name: String? 
var email: String? 

var completedRegister: Bool? 

var FULLUser: Bool? 

init(dictionary: [String: Any]) { 
    self.id = dictionary["id"] as? String 
    self.name = dictionary["name"] as? String 
    self.email = dictionary["email"] as? String 

    self.completedRegister = Bool((dictionary["completedRegister"] as? String)!) 

    self.FULLUser = Bool((dictionary["FULLUser"] as? String)!) 

} 
init() { 
    self.id = nil 
    self.name = nil 
    self.email = nil 

    self.completedRegister = nil 

    self.FULLUser = nil 

} 
} 

編輯爲亞太區首席技術官Matt

，如果我打印出來只是在打印字典用戶完成信息的同時。在一切結束。

Answer 1

問題是viewDidLoad()在打印"viewdidload user: \(user)"之前調用verifyUser()。打印前，verifyUser()中的所有內容都將完成（網絡通話除外）。

所以這裏是事件發生的對你的序列：

1. super.viewDidLoad()
2. verifyUser()叫
3. 打印語句是verifyUser()
4. 後衛聲明是verifyUser()
5. 打印在viewDidLoad()的說明
6. 每當通話結束 -
7. 打印在封閉的.observeSingleEventOf內super.viewDidAppear()

一切都將4後發生的一些點。如果您想在通話結束時執行某些操作，請將其置於關閉狀態。

像這樣：

ref.child("users").child(userID).observeSingleEvent(of: .value, with: { (snapshot) in 
    if let dictionary = snapshot.value as? [String: AnyObject] { 
     self.user = AppUser(dictionary: dictionary) 
     //***handle stuff that needs the user here 
     print(self.user) 
    } else { 
     //***handle getting no data for the user or data that is not [String: AnyObject] 
    } 
}) { (error) in 
    //***handle any errors here 
    print(error.localizedDescription) 
} 

，我添加了註釋是請求完成時將可能被稱爲地方的地方。

附註：如果你要使用APPUSER一個結構，只是確保你知道結構和類之間的差異。你可以有一個名爲APPUSER類，有兩個不同的inits這樣的：

class AppUser { 
    var id: String? 
    var name: String? 
    var email: String? 
    var completedRegister: Bool? 
    var FULLUser: Bool? 

    ///initialization from a dictionary 
    init(dictionary: [String: Any]) { 
     id = dictionary["id"] as? String 
     name = dictionary["name"] as? String 
     email = dictionary["email"] as? String 

     if let completed = dictionary["completedRegister"] as? String { 
      if completed == "true" { 
       completedRegister = true 
      } else if completed == "false" { 
       completedRegister = false 
      } 
     } 

     if let fullUser = dictionary["FULLUser"] as? String { 
      if fullUser == "true" { 
       FULLUser = true 
      } else if fullUser == "false" { 
       FULLUser = false 
      } 
     } 
    } 

    ///initialization without a dictionary 
    init() { 
     //dont need to set any variables because they are optional 
    } 
} 

---

let user1 = AppUser(dictionary: ["id": "12342", 
          "name": "John Doe", 
          "email": "email@email.com", 
          "completedRegister": "true", 
          "FULLUser": "true"]) 
    ///user1 properties: 
    id: Optional("12342") 
    - some: "12342" 
    name: Optional("John Doe") 
    - some: "John Doe" 
    email: Optional("email@email.com") 
    - some: "email@email.com" 
    completedRegister: Optional(true) 
    - some: true 
    FULLUser: Optional(true) 
    - some: true 

---

let user2 = AppUser() 
///user2 properties: none