I'm trying to retrieve the first name from a JSON database in Firebase. The structure of the database is as follows
users
|_Unique ID
|_firstName
|_lastName
|_userEmail
|_userID (Which I copied to the database from FirebaseAuth account creation)
I'm trying to display the firstName in a Welcome label. Here's how I have the view controller set up (Disclaimer, I'm a designer slowly learning how to work in XCode)
class HomeVC : UIViewController {
let rootRef = FIRDatabase.database().reference()
#IBOutlet weak var WelcomeLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
let userID = (FIRAuth.auth()?.currentUser?.uid)!
rootRef.child("users").child(userID).observeSingleEventOfType(
.Value, withBlock: { (snapshot) in
let firstName = snapshot.value!["firstName"] as! String
self.WelcomeLabel.text = firstName
})
}
}
I keep getting an error saying that "fatal error: unexpectedly found nil while unwrapping an Optional value". Any ideas? Do I happen to have my database structured incorrectly?
Related
I have created a dummy IOS Application to explain my questions well. Let me share it with all details:
There are 2 Pages in this dummy IOS Application: LoginPageViewController.swift and HomepageViewController.swift
Storyboard id values are: LoginPage, Homepage.
There is login button in Login page.
There are 3 labels in Homepage.
App starts with Login page.
And i have a class file: UserDetail.swift
And there is one segue from login page to home page. Segue id is: LoginPage2Homepage
UserDetail.swift file
import Foundation
class UserDetail {
var accountIsDeleted = false
var userGUID : String?
var userAge: Int?
}
LoginPageViewController.swift file
import UIKit
class LoginPageViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func loginButtonPressed(_ sender: UIButton) {
var oUserDetail = UserDetail()
oUserDetail.accountIsDeleted = true
oUserDetail.userAge = 38
oUserDetail.userName = "Dirk Kuyt"
UserDefaults.standard.set(oUserDetail, forKey: "UserCredentialUserDefaults")
UserDefaults.standard.synchronize()
performSegue(withIdentifier: "LoginPage2Homepage", sender: nil)
}
}
HomepageViewController.swift file
import UIKit
class HomepageViewController: UIViewController {
var result_userGUID = ""
var result_userAge = 0
var result_isDeleted = false
#IBOutlet weak var labelUserGuidOutlet: UILabel!
#IBOutlet weak var labelAgeOutlet: UILabel!
#IBOutlet weak var labelAccountIsDeletedOutlet: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
self.setVariablesFromUserDefault()
labelUserGuidOutlet.text = result_userGUID
labelAgeOutlet.text = String(result_userAge)
labelAccountIsDeletedOutlet.text = String(result_isDeleted)
}
func setVariablesFromUserDefault()
{
if UserDefaults.standard.object(forKey: "UserCredentialUserDefaults") != nil
{
// I need a help in this scope
// I have checked already: My UserDefault exists or not.
// I need to check type of the value in UserDefault if UserDefault is exists. I need to show print if type of the value in UserDefault is not belongs to my custom class.
// And then i need to cast UserDefault to reach my custom class's properties: userGUID, userAge, isDeleted
}
else
{
print("there is no userDefault which is named UserCredentialUserDefaults")
}
}
}
My purposes:
I would like to store my custom class sample(oUserDetail) in UserDefaults in LoginPageViewController with login button click action.
I would like to check below in home page as a first task: My UserDefault exists or not ( I did it already)
I would like to check this in home page as a second task: if my UserDefault exists. And then check type of the UserDefault value. Is it created with my custom class? If it is not. print("value of userdefault is not created with your class")
Third task: If UserDefault is created with my custom class. And then parse that value. Set these 3 variables: result_userGUID, result_userAge, result_isDeleted to show them in labels.
I get an error after I click the login button in Login Page. Can't I store my custom class in UserDefaults? I need to be able to store because I see this detail while I am writing it:
UserDefaults.standart.set(value: Any?, forKey: String)
My custom class is in Any scope above. Isn't it?
You can't store a class instance without conforming to NSCoding / Codable protocols
class UserDetail : Codable {
var accountIsDeleted:Bool? // you can remove this as it's useless if the you read a nil content from user defaults that means no current account
var userGUID : String?
var userAge: Int?
}
store
do {
let res = try JSONEncoder().encode(yourClassInstance)
UserDefaults.standard.set(value:res,forKey: "somekey")
}
catch { print(error) }
retrieve
do {
if let data = UserDefaults.standard.data(forKey:"somekey") {
let res = try JSONDecoder().decode(UserDetail.self,from:data)
} else {
print("No account")
}
}
catch { print(error) }
Why when I'am adding new data to firebase database appears duplicated in my app , but when I pull down to make refresh its back again not duplicated , I put a Screenshot of how data appears in my project simulator .This is how data appears in my project
This is my Code.
import UIKit
import FirebaseDatabase
import SDWebImage
import FirebaseAuth
class ViewController: UIViewController , UITableViewDataSource , UITableViewDelegate {
#IBOutlet weak var tableView: UITableView!
var Ref:FIRDatabaseReference?
var Handle:FIRDatabaseHandle?
var myarray = [Posts]()
var refresh = UIRefreshControl()
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
refresh.addTarget(self, action: #selector(ViewController.loadData), for: .valueChanged)
tableView.addSubview(refresh)
}
override func viewDidAppear(_ animated: Bool) {
loadData()
}
func loadData(){
self.myarray.removeAll()
Ref=FIRDatabase.database().reference()
Handle = Ref?.child("Posts").queryOrdered(byChild: "Des").queryEqual(toValue: "11").observe(.childAdded ,with: { (snapshot) in
if let post = snapshot.value as? [String : AnyObject]{
let img = Posts()
img.setValuesForKeys(post)
self.myarray.append(img)
print("##############################\(img)")
self.tableView.reloadData()
}
})
self.refresh.endRefreshing()
}
It appears self.refresh.endRefreshing() is being called outside the Firebase closure.
This is bad as that code will run before Firebase returns the data and reloads the tableView data.
Remember that Firebase is asynchronous and it takes time for the internet to get the data from the Firebase server to your app, so in-line code will usually execute before the code in the closure.
Also, the Handle is unneeded in this case unless you are using it elsewhere.
Ref?.child("Posts").queryOrdered(byChild: "Des").queryEqual(toValue: "11")
.observe(.childAdded ,with: { (snapshot) in
if let post = snapshot.value as? [String : AnyObject]{
let img = Posts()
img.setValuesForKeys(post)
self.myarray.append(img)
print("##############################\(img)")
self.tableView.reloadData()
}
self.refresh.endRefreshing()
})
Also, you may consider just removing the refreshing entirely as when you add an observer to a Firebase node (.childAdded) any time a child it added, your tableview will automatically refresh due to the code executed in the closure.
I read other stack overflow q&a's about this problem but it seems to be a tabBarController issue which I haven't found anything on.
I have a tabBarController with 3 tabs. tab1 is where I successfully send the info to Firebase. In tab2 I have tableView which successfully reads the data from tab1.
In tab2 my listener is in viewWillAppear. I remove the listener in viewDidDisappear (I also tried viewWillDisappear) and somewhere in here is where the problem is occurring.
override func viewDidDisappear(animated: Bool) {
self.sneakersRef!.removeAllObservers()
//When I tried using a handle in viewWillAppear and then using the handle to remove the observer it didn't work here either
//sneakersRef!.removeObserverWithHandle(self.handle)
}
Once I switch from tab2 to any other tab, the second I go back to tab2 the table data doubles, then if I switch tabs again and come back it triples etc. I tried setting the listener inside viewDidLoad which prevents the table data from duplicating when I switch tabs but when I send new info from tab1 the information never gets updated in tab2.
According to the Firebase docs and pretty much everything else I read on stackoverflow/google the listener should be set in viewWillAppear and removed in viewDidDisappear.
Any ideas on how to prevent my data from duplicating whenever I switch between back forth between tabs?
tab1
import UIKit
import Firebase
import FirebaseAuth
import FirebaseDatabase
class TabOneController: UIViewController{
var ref:FIRDatabaseReference!
#IBOutlet weak var sneakerNameTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
self.ref = FIRDatabase.database().reference()
}
#IBAction func sendButton(sender: UIButton) {
let dict = ["sneakerName":self.sneakerNameTextField.text!]
let usersRef = self.ref.child("users")
let sneakersRef = usersRef.child("sneakers").childByAutoID()
sneakersRef?.updateChildValues(dict, withCompletionBlock: {(error, user) in
if error != nil{
print("\n\(error?.localizedDescription)")
}
})
}
}
tab2
import UIKit
import Firebase
import FirebaseAuth
import FirebaseDatabase
class TabTwoController: UITableViewController{
#IBOutlet weak var tableView: UITableView!
var handle: Uint!//If you read the comments I tried using this but nahhh didn't help
var ref: FIRDatabaseReference!
var sneakersRef: FIRDatabaseReference?
var sneakerArray = [String]()
override func viewDidLoad() {
super.viewDidLoad()
self.ref = FIRDatabase.database().reference()
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
let usersRef = self.ref.child("users")
//Listener
self.sneakersRef = usersRef.child("sneakers")
//I tried using the handle
//---self.handle = self.sneakersRef!.observeEventType(.ChildAdded...
self.sneakersRef!.observeEventType(.ChildAdded, withBlock: {(snapshot) in
if let dict = snapshot.value as? [String:AnyObject]{
let sneakerName = dict["sneakerName"] as? String
self.sneakerArray.append(sneakerName)
dispatch_async(dispatch_get_main_queue(), {
self.tableView.reloadData()
})
}
}), withCancelBlock: nil)
}
//I also tried viewWillDisappear
override func viewDidDisappear(animated: Bool) {
self.sneakersRef!.removeAllObservers()
//When I tried using the handle to remove the observer it didn't work either
//---sneakersRef!.removeObserverWithHandle(self.handle)
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.sneakerArray.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("sneakerCell", forIndexPath: indexPath)
cell.textLabel?.text = sneakerArray[indexPath.row]
return cell
}
}
tab3 does nothing. I just use it as an alternate tab to switch back and forth with
The removeAllObservers method is working correctly. The problem you're currently experiencing is caused by a minor missing detail: you never clear the contents of sneakerArray.
Note: there's no need for dispatch_async inside the event callback. The Firebase SDK calls this function on the main queue.
The official accepted Answer was posted by #vzsg. I'm just detailing it for the next person who runs into this issue. Up vote his answer.
What basically happens is when you use .childAdded, Firebase loops around and grabs each child from the node (in my case the node is "sneakersRef"). Firebase grabs the data, adds it to the array (in my case self.sneakerArray), then goes goes back to get the next set of data, adds it to the array etc. By clearing the array on the start of the next loop, the array will be empty once FB is done. If you switch scenes, you'll always have an empty array and the only data the ui will display is FB looping the node all over again.
Also I got rid of the dispatch_async call because he said FB calls the function in the main queue. I only used self.tableView.reloadData()
On a side note you should subscribe to firebase-community.slack.com. That's the official Firebase slack channel and that's where I posted this question and vzsg answered it.
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
//CLEAR THE ARRAY DATA HERE before you make your Firebase query
self.sneakerArray.removeAll()
let usersRef = self.ref.child("users")
//Listener
self.sneakersRef = usersRef.child("sneakers")
//I tried using the handle
//---self.handle = self.sneakersRef!.observeEventType(.ChildAdded...
self.sneakersRef!.observeEventType(.ChildAdded, withBlock: {(snapshot) in
if let dict = snapshot.value as? [String:AnyObject]{
let sneakerName = dict["sneakerName"] as? String
self.sneakerArray.append(sneakerName)
//I didn't have to use the dispatch_async here
self.tableView.reloadData()
}
}), withCancelBlock: nil)
}
Thank for asking this question.
I have also faced same issue in past. I have solved this issue as follow.
1) Define array which contain list of observer.
var aryObserver = Array<Firebase>()
2) Add observer as follow.
self.sneakersRef = usersRef.child("sneakers")
aryObserver.append( self.sneakersRef)
3) Remove observer as follow.
for fireBaseRef in self.aryObserver{
fireBaseRef.removeAllObservers()
}
self.aryObserver.removeAll() //Remove all object from array.
I'm trying to retrieve data from my Firebase database, but I'm stuck at the database reference returning nil. However, I successfully can retrieve the UserID, so I don't think it's not properly connected to my database:
import UIKit
import Firebase
import FirebaseDatabaseUI
class LoggedInViewController: UIViewController {
var ref: FIRDatabaseReference!
let userid = FIRAuth.auth()?.currentUser?.uid
override func viewDidLoad() {
super.viewDidLoad()
UIDLabel.text = String((userid)!) // The Label shows the UID
reflabel.text = String(ref) // The Label shows "nil"
}
}
My goal is to retrieve data from the path using this method:
func getQuery() -> FIRDatabaseQuery {
let myTopPostsQuery = (ref.child("user-posts")).child(getUid()))
return myTopPostsQuery
}
But obviously this doesn't work since I'm getting an error because of the nil reference.
In viewDidLoad use FIRDatabase.database().reference()
override func viewDidLoad() {
super.viewDidLoad()
self.ref = FIRDatabase.database().reference()
//....
}
Currently working with two view controllers and a swift file dealing with the details of a store such as the phone number. There is a main ViewController and a DetailsViewController.
I currently acquire data from google places api and am able to successfully store the values in a PlaceDetails Class. Testing out the data - I am able to print to the console. However, when I try to assign a value taken from the API to a UILabel the application crashes and shows that the value of the property is nil. I am not sure why this is the case. I feel in the two view controllers I am instantiating the PlaceDetails class correctly and accessing it's properties correctly but there is something I am not aware of that is going wrong.
class ViewController: UIViewController
{
let placeDetails = PlaceDetails()
let detailsVC = DetailsViewController()
func tapLabel( sender: UITapGestureRecognizer )
{
// print statement successfully prints out the stored value as - Optional("1 888-555-5555")
print(placeDetails.phoneNumber)
// assigning value to label causes a crash stating value is nil
detailsVC.phoneNumberLabel.text = placeDetails.phoneNumber!
self.performSegueWithIdentifier("showDetailsVC", sender: self)
}
}
class DetailsViewController: UIViewController
{
#IBOutlet weak var phoneNumberLabel : UILabel!
let placeDetails = PlaceDetails()
override func viewDidLoad()
{
super.viewDidLoad()
//This approach does not cause a crash but outputs nil to the console for both the print statement and the assignment statement
print(placeDetails.phoneNumber)
phoneNumberLabel.text = placeDetails.phoneNumber!
}
}
class PlaceDetails
{
override init()
{
super.init()
}
var phoneNumber : String? //viewcontroller actions give this class property its value
}
You need to assign placeDetails to your destination view controller in prepareForSegue. I know you aren't doing this as you have created placeDetails as a let constant rather than a variable so it can't ever change from the empty PlaceDetails you originally assign.
You should declare it as an optional variable and then unwrap it properly when you use it;
class ViewController: UIViewController
{
let placeDetails = PlaceDetails()
func tapLabel( sender: UITapGestureRecognizer )
{
self.performSegueWithIdentifier("showDetailsVC", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if (segue.identifier == "showDetailsVC") {
let destVC = segue.destinationViewController as! DetailsViewController
destVC.placeDetails = self.placeDetails
}
}
}
class DetailsViewController: UIViewController
{
#IBOutlet weak var phoneNumberLabel : UILabel!
var placeDetails: PlaceDetails?
override func viewWillAppear(animated: Bool)
{
super.viewWillAppear(animated)
if let placeDetails = self.placeDetails {
if let phoneNumber = placeDetails.phoneNumber {
self.phoneNumberLabel.text = phoneNumber
}
}
}
}
You can't use the value in viewDidLoad as this method will execute before the property has been set; the view controller is loaded before prepareForSegue is called, so viewWillAppear is a better place.
Try to cast your phoneNumber in a string.
detailsVC.phoneNumberLabel.text = String(placeDetails.phoneNumber!)
Also, the nil value could come from the encoding method of the response of the API.
EDIT
I think you have to set the text of your UILabel in the viewDidLoad() method of your showDetailsVC. Declare a string variable in showDetailVC, and then pass your placeDetails.phoneNumber variable to the string you just declare. (Instead of directly set the text in the tapLabel() method). Then in your
showDetailVC set the text to your UILabel in the viewDidLoad()