I've been trying to remove observers for a while but somehow I have never succeeded. I've checked other posts here but I can’ｔ find the reason why.
Here are my codes:
var ref: DatabaseReference!
let timeStamp: Double = NSDate().timeIntervalSince1970
override func viewDidLoad() {
super.viewDidLoad()
self.ref = Database.database().reference()
guard let userId = Auth.auth().currentUser?.uid else { return }
self.ref.child("users").child(userId).child("contactList").observe(.value, with: { (snapshot) in
guard let children = snapshot.value as? [String: Any] else { return }
for child in children {
guard let dictionary = child.value as? [String: Any] else { return }
guard let timeStamp = dictionary["timeStamp"] as? String else { return }
guard let timeStampDouble = Double(timeStamp) else { return }
if timeStampDouble > self.timeStamp {
self.navigationController?.pushViewController(HomeController(), animated: true)
}
}
}) { (err) in
print("Failed to fetch user: ", err)
}
}
deinit {
self.ref.child("users").removeAllObservers()
}
I would appreciate any advise!
Calling removeAllObservers on a node, removes all observers from that node only. It doesn't remove observers from child nodes.
So your code:
self.ref.child("users").removeAllObservers()
This only removes the observers from users. It does not remove the observers from users/$userId/contactList. To remove the latter, you will have to call removeAllObservers on that specific node, which means you'll need to track what nodes you have attached observers to.
Related
I am trying to read data from media when data is updated on /media node, but .observe(.childAdded is not called.
For example, I update data at /media/-LKN1j_FLQuOvnhEFfao/caption , but I never receive the event in observeNewMedia .
I can read the data with no problem the first time when ViewDidLoad completes.
The first step is to download the user data, second is to get the locality from currentUser and the last step is to attach a listener .childAdded on media.
I suspect that the event is not triggered because fetchMedia is called inside DDatabaseRReference.users(uid: uid).reference().observe(.value
media
-LKNRdP4ZsE3YrgaLB30
caption: "santa"
mediaUID: "-LKNRdP4ZsE3YrgaLB30"
locality: "barking"
users
Q6Dm3IMLNLgBH3ny3rv2CMYf47p1
media
-LKNReJCxgwtGRU6iJmV: "-LKNRdP4ZsE3YrgaLB30"
email: "john#gmail.com"
locality: "barking"
//enables the programmer to create references to different childs in Firebase
enum DDatabaseRReference {
case root
case users(uid:String)
case media //to store photos
func reference() -> DatabaseReference {
return rootRef.child(path)
}
//return root reference to our database
private var rootRef: DatabaseReference {
return Database.database().reference()
}
private var path: String {
switch self { //self is the enum DDatabaseReference
case .root:
return ""
case .users(let uid):
return "users/\(uid)"
case .media:
return "media"
}
}
}//end of enum DatabaseReference
class NewsfeedTableViewController: UITableViewController {
override func viewDidLoad() {
super.viewDidLoad()
//observe ~/users/uid
DDatabaseRReference.users(uid: uid).reference().observe(.value, with: { (snapshot) in
DispatchQueue.main.async {
if let userDict = snapshot.value as? [String : Any] {
self.currentUser = UserModel(dictionary: userDict)
self.fetchMedia()
self.tableView.reloadData()
}
}
})
}
func fetchMedia() {
Media.observeNewMedia((currentUser?.locality)!) { (newMedia) in
//check if newly downloaded media is already in media array
if !self.media.contains(newMedia) {
self.media.insert(newMedia, at: 0)
self.tableView.reloadData()
}else {
//remove old media and add the newly updated one
guard let index = self.media.index(of: newMedia) else {return}
self.media.remove(at: index)
self.media.insert(newMedia, at: 0)
self.tableView.reloadData()
}
}
}
}//end of NewsfeedTableViewController
class Media {
class func observeNewMedia(_ userLocality: String, _ completion: #escaping (Media) -> Void) {
DDatabaseRReference.media.reference().queryOrdered(byChild: "locality").queryEqual(toValue: userLocality).observe(.childAdded, with: { snapshot in
guard snapshot.exists() else {
print("no snap ")
return}
print("snap is \(snapshot)")
let media = Media(dictionary: snapshot.value as! [String : Any])
completion(media)
})
}
} //end of class Media
Let's first update the structure so make it more queryable
assume a users node
users
-Q6Dm3IMLNLgBH3ny3rv2CMYf47p1 //this is each users uid
email: "john#gmail.com"
locality: "barking"
and a media node that contains media for all users
media
-abcdefg12345 //node created with childByAutoId
caption: "santa"
for_uid: -Q6Dm3IMLNLgBH3ny3rv2CMYf47p1 //matches the uid in the /users node
Then our main viewController which contains a reference to Firebase and logs the user in
class ViewController: UIViewController {
var ref: DatabaseReference!
override func viewDidLoad() {
super.viewDidLoad()
self.ref = Database.database().reference()
//log user in which will populate the Auth.auth.currentUser variable
}
.
.
.
We need an object to store the media in and then an array to hold those objects
class MediaClass {
var key = ""
var caption = ""
init(k: String, c: String) {
self.key = k
self.caption = c
}
}
var mediaArray = [MediaClass]()
then set up the observers which will add, update or remove from the array when media for this user is added, changed or removed.
let thisUid = Auth.auth().currentUser?.uid
let mediaRef = self.ref.child("media")
let queryRef = mediaRef.queryOrdered(byChild: "for_uid").queryEqual(toValue: thisUid)
queryRef.observe(.childAdded, with: { snapshot in
let dict = snapshot.value as! [String: Any]
let key = snapshot.key
let caption = dict["caption"] as! String
let m = MediaClass.init(k: key, c: caption)
self.mediaArray.append(m)
self.tableView.reloadData()
})
queryRef.observe(.childChanged, with: { snapshot in
let dict = snapshot.value as! [String: Any]
let key = snapshot.key
let caption = dict["caption"] as! String
let index = self.mediaArray.index { $0.key == key } //locate this object in the array
self.mediaArray[index!].caption = caption //and update it's caption
self.tableView.reloadData()
})
//leaving this an an exercise
queryRef.observe(.childRemoved....
Note we added .childAdded, .childChanged and .childRemoved events to the media node via a query so the only events the app will receive are the ones that pertain to this user.
Also note there's no error checking so that needs to be added.
I am beginner and I would like to use swift as my programming language.
user can add register users and transfer money to each other, therefore when user type the photo number and email, the app can check if the typed number is registered in the firebase system
Any simple way to search if the user exist, thanks a lot
Here's the structure of the database
var ref: DatabaseReference!
var tref: DatabaseReference!
var handle : DatabaseHandle!
var usersArray = [NSDictionary?]()
var filteredUsers = [NSDictionary?]()
var user : NSDictionary?
override func viewDidLoad() {
super.viewDidLoad()
self.picker.isHidden = true
tref = Database.database().reference()
ref = Database.database().reference()
self.handle = self.ref?.child("users").child((Auth.auth().currentUser?.uid)!).child("contact").observe(.childAdded, with: { (snapshot) in
if let item = snapshot.value as? String {
self.pickerdata.append(item)
self.picker.reloadAllComponents()
}
})
self.picker.delegate = self
self.picker.dataSource = self
tref.child("users").queryOrdered(byChild: "phone").observe(.childAdded, with: {(snapshot) in
self.usersArray.append(snapshot.value as? NSDictionary)
})
print(usersArray.count)
}
#IBAction func ContactChange(_ sender: UITextField) {
filteredContent(searchText: contactText.text!)
print(filteredUsers.count)
print(usersArray.count)
print("ARRAY")
}
func filteredContent(searchText: String){
self.filteredUsers = self.usersArray.filter{ user in
let username = user!["phone"] as? String
return (username?.lowercased().contains(searchText.lowercased()))!
}
}
func findUsers(text: String){
self.handle = ref.child("users").queryOrdered(byChild: "phone").queryStarting(atValue: contactText.text!).queryEnding(atValue: contactText.text!+"\u{f8ff}").observe(.value, with: { snapshot in
if let item = snapshot.value as? String {
self.contact.append(item)
} else{
print("error")
}
})
}
The code above doesn't work much. Thanks so much for helping
The question is a little unclear but I think what the OP is asking is:
how to see if a user exists by their phone number?
If that's what's being asked, a node can be retrieved by query'ing for a child of that node. For example, let's create a query on the users node to find the child that contains the name: Kam querying by phone
let usersRef = firebaseRef.child("users")
let query = usersRef.queryOrdered(byChild: "phone").queryEqual(toValue: "2330504")
query.observeSingleEvent(of: .value) { (snapshot) in
if snapshot.exists() {
//need to iterate in case we find more than one match
for child in snapshot.children {
let snap = child as! DataSnapshot
let dict = snap.value as! [String: Any]
let name = dict["name"] as! String
print("found \(name)")
}
} else {
print("not found")
}
}
When this code is run it would print
found Kam
assuming the phone number is 2330504
I have two observers, the second observer is dependent on the first observers value. I can't seem to get the first observer to work, I am not getting any errors on Xcode. The first function has to check the Users profile for information and then use that information to search for different information in the database. Here is my code:
func loadposts() {
ref = Database.database().reference()
let trace = Performance.startTrace(name: "test trace")
trace?.incrementCounter(named:"retry")
let userID = Auth.auth().currentUser?.uid
print(userID!)
ref.child("Users").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
// Get user value
let value = snapshot.value as? NSDictionary
let one1 = value?["Coupon Book"] as? String ?? ""
print("one1: \(one1)")
self.bogus.set(one1, forKey: "bogus")
}) { (error) in
print(error.localizedDescription)
}
delay(0.1) {
print("bogus: \(self.bogus.string(forKey: "bogus"))")
Database.database().reference().child("Coupons").child(self.bogus.string(forKey: "bogus")!).observe(.childAdded) { (Snapshot : DataSnapshot) in
if let dict = Snapshot.value as? [String: Any] {
let captiontext = dict["company name"] as! String
let offerx = dict["offer count"] as! String
let logocomp = dict["logo"] as! String
let actchild = dict["childx"] as! String
let post = Post(captiontext: captiontext, PhotUrlString: actchild, offertext: offerx, actualphoto: logocomp)
self.posts.append(post)
self.tableview.reloadData()
print(self.posts)
}
}
}
trace?.stop()
}
Any help is appreciated.
self.bogus.string(forKey: "bogus"))" is nil because observeSingleEvent is an async method, so to get the required results you need to call the second observer inside the first observer or you can use the completion handler
You can use the completionHandler like this:
guard let uid = Auth.auth().currentUser?.uid else {
return
}
func firstObserverMethod(completionCallback: #escaping () -> Void) {
ref.child("Users").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
// Get user value
if let value = snapshot.value as? [String: Any] {
let one1 = value["Coupon Book"] as? String
print("one1: \(one1)")
self.bogus.set(one1, forKey: "bogus")
completionCallback()
}
}) { (error) in
print(error.localizedDescription)
}
}
Now using the above method:
firstObserverMethod {
print("bogus: \(self.bogus.string(forKey: "bogus"))")
guard let bogusString = self.bogus.string(forKey: "bogus") else {
print("bogus is not set properly")
return
}
Database.database().reference().child("Coupons").child(bogusString).observe(.childAdded) { (Snapshot : DataSnapshot) in
if let dict = Snapshot.value as? [String: Any] {
let captiontext = dict["company name"] ?? ""
let offerx = dict["offer count"] ?? ""
let logocomp = dict["logo"] ?? ""
let actchild = dict["childx"] ?? ""
let post = Post(captiontext: captiontext, PhotUrlString: actchild, offertext: offerx, actualphoto: logocomp)
self.posts.append(post)
DispatchQueue.main.async {
self.tableview.reloadData()
}
print(self.posts)
}
}
}
Note: You should use optional binding to get the values from optional
Since you are using the result of the 1st observer in the reference of your 2nd observer, it's a very bad idea to add the 2nd observer right below the first observer. And adding a delay won't be a viable solution : these two calls are asynchronous, which means that the reason why you are not getting might very likely be because the 2nd observer is triggered even before the 1st has returned any data.
The solution here, would be using a completion handler, or you could just incorporate your 2nd observer inside the completion block of the 1st, to be make sure that the proper order (1st observer -> 2nd observer) will always be respected.
It would look somehow like this:
func loadposts() {
// ...
// 1st Observer here
ref.child("Users").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
// Get your value here
guard let one1 = snapshot.childSnapshot(forPath: "Coupon Book").value as? String else { return }
// 2nd Observer here. Now you can use one1 safely:
Database.database().reference().child("Coupons").child(one1).observe(.childAdded) { (Snapshot : DataSnapshot) in
// ...
}
})
}
Now, a couple of things that you could also improve in your code, while not directly related to the question:
I would suggest you to make use of guard statements instead force-unwrapping, which may end up in crashing your app at some point.
For example, you could check whether your current user exist or not like so:
guard let currentUserID = Auth.auth().currentUser?.uid else {
return
}
// Now you can use safely currentUserID
Also, when you try to get the data out of the snapshot, it's not a good idea either, to use force-casting. You would better write it in this way:
yourRef.observeSingleEvent(of: .value, with: { (snapshot) in
for child in snapshot.children.allObjects as! [DataSnapshot] {
guard let text = child.childSnapshot(forPath: "text").value as? String, let somethingElse = child.childSnapshot(forPath: "otherValue").value as? NSNumber else {
return
}
// And so on, depending of course on what you have in your database.
}
In my Firebase database, I have children containing Unix times, and I'm querying by times that occur after the current time. I'm putting the data of each child which matches that criteria into a UICollectionView. When the current time surpasses the time of one of the children, I want for the child to expire, and to get removed from the UICollectionView. Currently, it isn't getting removed until I restart the app. Here is some of the code:
// in viewDidLoad
self.events_query = Database.database().reference().child("events").queryOrdered(byChild: "end-time").queryStarting(atValue: Date().timeIntervalSince1970)
// in viewWillAppear
func observeAllEvents() {
self.events_query.observe(.value, with: { (snapshot) in
guard let eids_dict = snapshot.value as? [String : AnyObject] else { return }
let eids = Array(eids_dict.keys)
for eid in eids {
print(eid)
}
Event.getAllEvents(with: eids, ref: self.events_query.ref, completion: { (events) in
if let feed_datasource = self.datasource as? EventFeedDatasource {
feed_datasource.events = events
}
DispatchQueue.main.async {
self.collectionView?.reloadData()
}
})
})
}
// in viewDidDisappear
self.events_query.removeAllObservers()
Here's the function getAllEvents:
static func getAllEvents(with eids: [String], ref: DatabaseReference, completion: #escaping (_ events: [Event]) -> Void) {
var events = [Event]()
let dispatch_groups = [DispatchGroup(), DispatchGroup()]
for eid in eids {
dispatch_groups[0].enter()
ref.child(eid).observeSingleEvent(of: .value, with: { (snapshot) in
guard let dictionary = snapshot.value as? [String : AnyObject] else { return }
dispatch_groups[1].enter()
// I'm not including `load` because all it does is parse the snapshot
Event.load(with: dictionary, completion: { (event) in
events.append(event)
dispatch_groups[1].leave()
})
dispatch_groups[0].leave()
})
}
dispatch_groups[0].notify(queue: DispatchQueue.main) {
dispatch_groups[1].notify(queue: DispatchQueue.main) {
completion(events)
}
}
}
I'm trying to run a function to be able to retrieve data from the realtime database with Firebase, however whenever I run the function; the observerSingleEvent part of my function will not run, I have tried putting a print statement within and it is not being run nor is the fields being read to the variable, any help would be beneficial.
func checkIfNewDay() -> Bool {
print(self.currDate)
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
let userID = FIRAuth.auth()?.currentUser?.uid
print("outside function")
ref.child("user").child(userID!).child("dates").observeSingleEvent(of: .value, with: { (snapshot) in
// Get user value
print("inside function")
let value = snapshot.value as? NSDictionary
print("just to make sure its going inside the function. Delete after")
self.lastDate = value?["lastSaveDate"] as? String ?? "Date Invalid"
self.newLastDate = String(self.lastDate)
if self.newLastDate != "Date Invalid" {
print(self.lastDate)
} else {
print("Error, date not able to be recieved from the database")
self.catchGetDateError = true
self.saveCurrentDate()
}
})
if (!self.catchGetDateError) {
print(self.newLastDate, "newLastDate")
print(self.currentDate, "currentDate")
if (self.newLastDate == self.currentDate) {
print("Day has not moved on.")
return false
} else {
print("Day has moved on!")
return true
}
}
return true
}
I apologise for the really long function - was quite a weird one to write.
From comments I think I have understood, what do you want.
For getting this results like sync, you need to implement escaping. Like this:
func checkIfNewDay(completion: #escaping (_ isNew: Bool) -> Void) {
print(self.currDate)
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
let userID = FIRAuth.auth()?.currentUser?.uid
print("outside function")
ref.child("user").child(userID!).child("dates").observeSingleEvent(of: .value, with: { (snapshot) in
// Get user value
print("inside function")
let value = snapshot.value as? NSDictionary
print("just to make sure its going inside the function. Delete after")
self.lastDate = value?["lastSaveDate"] as? String ?? "Date Invalid"
self.newLastDate = String(self.lastDate)
if self.newLastDate != "Date Invalid" {
print(self.lastDate)
if (self.newLastDate == self.currentDate) {
print("Day has not moved on.")
completion(false)
} else {
print("Day has moved on!")
completion(true)
}
} else {
print("Error, date not able to be recieved from the database")
self.catchGetDateError = true
self.saveCurrentDate()
completion(false)
}
})
}
So, now you can use your func:
checkIfNewDay(completion: { isNew in
// do whatever you want. isNew will have info, that you need.
})
You should have it, because .observe functions work async. You should understand the idea.
Hope it helps.