如何从从 Firebase 检索信息的闭包中传递数据？

Question

我正在尝试将从我的 firebase 数据库中检索到的数据传递到我的单例字段中。数据是通过闭包接收的，在那个闭包中，我将一些数据传递到我的单例属性中。如果我在闭包内打印数据结构（在分配了所有内容之后），我会得到我期望的输出，但是如果我在应该传入所有数据之后在初始化程序的末尾打印它，它是空的。

import Foundation
import Firebase

class EmployeeList {
    static let sharedInstance = EmployeeList()
    var employeeDictionary: [String: [EmployeeData]]
    var ref: DatabaseReference!

    private init() {
        employeeDictionary = [String: [EmployeeData]]()
        ref = Database.database().reference()

        ref.child("employeeList").observeSingleEvent(of: .value, with: { snapshot in
            if let dictionary = snapshot.value as? [String: [String: AnyObject]] {
                for subsection in dictionary {
                    var subsectionEmployees: [EmployeeData] = []

                    for item in subsection.value {
                        self.ref.child("employeeList/\(subsection.key)/\(item.key)").observeSingleEvent(of: .value, with: { employeeSnapshot in
                            let employeeObject = EmployeeData(snapshot: employeeSnapshot)
                            subsectionEmployees.append(employeeObject)
                            self.employeeDictionary[subsection.key] = subsectionEmployees
                            //print(self.employeeDictionary) This print statement prints out the expected data every time another employee is appended
                        })
                    }
                }
            }
            //print(self.employeeDictionary) This print statement prints an empty data structure
        })
    }
}

Answer 1

从 Firebase 获取数据如下

var messagedata = [String:AnyObject]()

 let databaseReff = Database.database().reference().child("message")

 databaseReff.queryOrdered(byChild: "fromId").queryEqual(toValue: self.recieverId).observe(.value, with: { snapshot in
      if snapshot.exists(){
           self.messagedata = snapshot.value! as! [String : AnyObject]        
           self.getAllMessagesSent(snapshot: self.messagedata)
      } else 
           self.getAllMessagesSent(snapshot: self.messagedata) //Function Created
      }
 })

将从 Clousre 获取的数据传递给字典，然后将该字典传递给函数，然后执行您想做的任何事情或使用转义块

func getAllMessagesSent(snapshot: [String:AnyObject]) {
     //data is here
}