我正在尝试从UITableView中的Firebase数据库中检索数据它的工作正常，但我需要提供另一个ViewController并将其关闭并返回到我的TableView数据重复
这是我的代码：
import UIKit
import Firebase
import FirebaseDatabase
class AddEditRosterViewController: UIViewController {
// MARK: - Properties
var students = [Student]()
var tempStudents = [Student]()
var studentsDict = [String:[Student]]()
var sectionLetters = [String]()
var allLetters = ["A" , "B" , "C" , "D" , "E" , "F" , "G" , "H" , "I" , "J" , "K" , "L" , "M" , "N" , "O" , "P" , "Q" , "R" , "S" , "T" , "U" , "V" , "W" , "X" , "Y" , "Z"]
var sections = [String]()
var ref:DatabaseReference!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
// set databse ref
ref = Database.database().reference()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if self.studentsDict.count == 0
{
self.retrivedData()
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillAppear(animated)
self.studentsDict.removeAll()
self.students.removeAll()
self.tempStudents.removeAll()
self.sections.removeAll()
}
func retrivedData()
{
showLoaderForController(self)
StudentsViewModel.shared.getAllUsers(completion: { res , data in
hideLoaderForController(self)
if res == true
{
self.students = data
self.tempStudents = data
for student in self.students
{
let firstname = student.firstname!
let key = firstname.substring(to: 1)
let lower = key.lowercased()
if var wordValues = self.studentsDict[lower]
{
wordValues.append(student)
self.studentsDict[lower] = wordValues
}else
{
self.studentsDict[lower] = [student]
}
}
self.sectionLetters = [String] (self.studentsDict.keys).sorted()
self.tableView.reloadData()
}
self.tableView.reloadData()
})
extension AddEditRosterViewController : UITableViewDelegate , UITableViewDataSource
{
// MARK: - Table view data source
func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
var numOfSections: Int = 0
if self.sectionLetters.count > 0
{
tableView.separatorStyle = .singleLine
numOfSections = self.sectionLetters.count
tableView.backgroundView = nil
}
else
{
let noDataLabel: UILabel = UILabel(frame: CGRect(x: 0, y: 0, width: tableView.bounds.size.width, height: tableView.bounds.size.height))
noDataLabel.text = "There are no students found"
noDataLabel.font = UIFont(name: "Avenir Next Medium", size: 19)!
noDataLabel.textColor = UIColor.black
noDataLabel.textAlignment = .center
tableView.backgroundView = noDataLabel
tableView.separatorStyle = .none
}
return numOfSections
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
let wordKey = self.sectionLetters[section]
if let wordValues = self.studentsDict[wordKey]
{
return wordValues.count
}
return 0
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "userCell", for: indexPath) as! SearchUserTableViewCell
let wordKey = sectionLetters[indexPath.section]
if let students = self.studentsDict[wordKey]
{
let student = students[indexPath.row]
cell.fullName.text = "\(student.firstname!) \(student.lastname!)"
cell.location.text = student.currentLocation.location!
cell.userImage.sd_setImage(with: URL(string: student.image!), placeholderImage: #imageLiteral(resourceName: "Profile"))
}
return cell
}
}
以及此处的控制器方法
func getAllUsers(completion:@escaping(_ result:Bool , _ data : [Student]) -> () )
{
ref = Database.database().reference()
// array to save values
var array = [Student]()
ref.child("students").observe(.value, with: { snapshot in
if snapshot.exists()
{
// snapshots
for snap in snapshot.children {
let userSnap = snap as! DataSnapshot
// let uid = userSnap.key //the uid of each user
let userDict = userSnap.value as! [String:AnyObject]
let student = Student()
student.id = userSnap.key
student.firstname = userDict["first_name"] as? String
student.lastname = userDict["last_name"] as? String
student.email = userDict["email"] as? String
student.mobile = userDict["mobile"] as? String
student.dorm = userDict["dorm"] as? String
student.form = userDict["form"] as? Int
student.gender = userDict["gender"] as? String
student.image = userDict["profile_picture"] as? String
student.currentLocation.location = userDict["current_location"] as? String
student.grade = userDict["grade"] as? Int
array.append(student)
}
completion(true, array)
}else
{
completion(false, [])
}
})
}
每次视图didAppear
时，我只需要调用retrivedData（）但首先删除旧数据并替换为新数据
答案 0 :(得分：0)
调用firebase db observer时，从控制器方法中删除数组中的所有对象，然后在解析后追加。
像this一样。
答案 1 :(得分：0)
在添加另一个之前，请尝试删除观察者。似乎当发生任何变化时，观察者函数被调用不止一次。
RestTemplate还要确保在附加任何其他数据之前删除数据。