如何正确读取viewDidLoad（）func上的Firebase数据库？

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) 
    } 
} 

控制台：

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)) 

的问题很简单。有人可以解释在“验证用户名”和“用户”之间打印"print("viewDidLoad user:....")"与数据库信息的可能性吗？

问题是，当我尝试获取viewDidLoad上的用户信息由于某种原因，该函数没有获取信息，所以值仍然为零。这是时间问题吗？

我试图把一个循环功能verifyUser（）之后，但它从来没有得到

out: 

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

所以......这就是问题

谢谢！

编辑阿纳斯·门哈尔 这是我的结构。为什么做一个NSObject会更好？ 我做了一个结构，因为我可以做两inits不同（一个空）和NSObject的没让我出于某种原因

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 

} 
} 

编辑为亚太区首席技术官Matt

，如果我打印出来只是在打印字典用户完成信息的同时。在一切结束。

Answer 1

问题是viewDidLoad()在打印"viewdidload user: \(user)"之前调用verifyUser()。打印前，verifyUser()中的所有内容都将完成（网络通话除外）。

所以这里是事件发生的对你的序列：

1. super.viewDidLoad()
2. verifyUser()叫
3. 打印语句是verifyUser()
4. 后卫声明是verifyUser()
5. 打印在viewDidLoad()的说明
6. 每当通话结束 -
7. 打印在封闭的.observeSingleEventOf内super.viewDidAppear()

一切都将4后发生的一些点。如果您想在通话结束时执行某些操作，请将其置于关闭状态。

像这样：

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) 
} 

，我添加了注释是请求完成时将可能被称为地方的地方。

附注：如果你要使用APPUSER一个结构，只是确保你知道结构和类之间的差异。你可以有一个名为APPUSER类，有两个不同的inits这样的：

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