My code goes as followed.
Once I get to the part where I am writing to the database it seems to skip over ContestName. Then it will record the contestdescription and user to the database. If I put contestDescription first before contestName then the contestDescription is missed but the name gets stored. Really funky bug. Any help would be appreciated.
NOTE: I tried a sleep but that didn't help at all.
#IBAction func SubmitContest(_ sender: Any) {
//Convert to text
let contesttitle = ContestName.text;
let contestdescript = ContestDescription.text;
//Some Firebase Stuff
let userID = Auth.auth().currentUser?.uid
let contestRef = ref.child("craftType").child("Custom")
let thisContest = contestRef.childByAutoId()
//Store to firebase
//Whatever one is first is not making it to firebase database
thisContest.setValue(["ContestName": contesttitle])
thisContest.setValue(["ContestDescription": contestdescript])
thisContest.child("User").setValue(userID)
}
Calling setValue on a location replaces all existing data at that location. So in this snippet:
thisContest.setValue(["ContestName": contesttitle])
thisContest.setValue(["ContestDescription": contestdescript])
The second line is replacing whatever the first line writes.
You should either combine the two:
thisContest.setValue(["ContestName": contesttitle, "ContestDescription": contestdescript])
Or use updateChildValues (which doesn't replace the entire data at the location, but only at the properties you specify):
thisContest.updateChildValues(["ContestName": contesttitle])
thisContest.updateChildValues(["ContestDescription": contestdescript])
Related
I have an app that uses a snapshot listener to listen to data in a particular document. However, when a field in the document is updated, the data is read 7-10x over. Never read once, and never read the number of fields that are in my document, it always seems to be an arbitrary number. Also, when the read data prints out, it seems like every printout is the same except for a couple of fields that I'm not setting (like an array prints out "<__NSArrayM 0x282d9f240>" but the number changes on each print). As a result, minimal usage of my app is causing 5-10k reads. I'm trying to reduce the number of reads and I don't know exactly how, but the app has to read as data is updated, but my two questions are:
when I print the data from the listener, does each data print out signify a separate read operation? and
is there any way for the listener to be alerted of the update but wait to actually perform the read until the data is updated, then perform one read instead of multiple reads every time any field is updated? Or another strategy to reduce reads when multiple writes occur?
Not sure if this is helpful, but here is the code I'm using to perform the read...its pretty much the standard code from the firestore sdk:
env.db.collection(env.currentSessionCode!).document(K.FStore.docName).addSnapshotListener { [self] documentSnapshot, error in
guard let document = documentSnapshot else {
print("Error fetching snapshot: \(error!)")
return
}
guard let data = document.data() else {
print("Document data was empty.")
return
}
self.env.data1 = data[K.FStore.data1] as? String ?? "????"
self.env.data2 = data[K.FStore.data2] as? String ?? "????"
self.env.data3 = data[K.FStore.data3] as? [String] ?? ["????"]
self.env.data4 = data[K.FStore.data4] as? [String] ?? ["????"]
self.env.data5 = data[K.FStore.data5] as? Double ?? 0
self.env.data6 = data[K.FStore.data6] as? Double ?? 0
self.env.data7 = data[K.FStore.data7] as! Bool
self.env.data8 = data[K.FStore.data8] as! Bool
print("Current data: \(data)")
Update - For clarification, the way I have been updating my data to firebase is with a environment object, and using "didSet" when the new data is changed/updated in the environment to update it on firebase...I think this might be the root of the problem, as the function called on didSet runs 4-5 times each time it is called...
relevant code:
#Published var data1: String {
didSet {
postValuesToFB(fb: K.FStore.data1, string: data1)
}
}
func postValuesToFB(fb: String, string: String) {
guard let code = currentSessionCode else {
fatalError("Error - Connection Check - no value for current session code in Global Env")
}
let docRef = db.collection(code).document(K.FStore.docName)
docRef.getDocument { document, _ in
guard let document = document else {
return
}
if document.exists {
let session = self.db.collection(code).document(K.FStore.docName)
session.updateData([
fb: string,
K.FStore.dateLastAccessed: FieldValue.serverTimestamp(),
])
return
}
}
}
Based on your comments, it sounds as if you've written no code to remove a listener after it's been added. Based on this, it's relatively safe to assume that your code could be adding many listeners over time, and each one is getting called for each change.
You should take a moment to think about the architecture of your app and figure out when is the appropriate time to remove listeners when they're no longer needed. Usually this corresponds with the lifecycle of whatever component is responsible for display of the data from the query. Review the documentation for getting realtime updates, especially the section on detaching a listener. It's up to you to determine the right time to remove your listener, but you definitely don't want to "leak" a listener as you are now.
A common source of unexpected read charges for developers who are new to Firestore is the Firebase console itself. When that console displays Firestore content, you are charged for those read too. To ensure you measure the impact of your code correctly, test it with the Firebase console closed.
when I print the data from the listener, does each data print out signify a separate read operation?
Not really. You get charged for a document read, when the document is read on your behalf on the server. You are not charted for printing the same DocumentSnapshot multiple times.
is there any way for the listener to be alerted of the update but wait to actually perform the read until the data is updated
Nope. To know the document has changed, the server needs to read it. So that requires a charged read operation.
I have a chat system inside my app. When the user presses send to send the message data to different nodes inside the database -it works fine. The issue I'm having is since I'm using fan out I generate the .childByAutoIdkey before the data is sent. The user presses a send button to start the process but it's always the same exact .childByAutoId key so I'm just overwriting the previous message data. If the user pops the vc and comes back to it then a new key is created but obviously that's terrible ux for a messaging system?
How can I generate different .childByAutoId keys every time the user presses send to fan out?
#obj func sendMessageButtonPressed() {
// ***here's the problem, every time they press send, it's the same exact childByAutoId().key so I'm just overwriting the previous data at the messages/messageId path
guard let messageId = FirebaseManager.Database.database().reference().child("messages")?.childByAutoId().key else { return }
var messageIdDict: [String: Any] = [messageId: "1"]
var messageDict = [String: Any]() // has the fromId, toId, message, and timeStamp on it
let messageIdPath = "messages/\(messageId)"
let fromIdPath = "user-messages/\(currentUserId)"
let toIdPath = "user-messages/\(toId)"
var fanOutDict = [String: Any]()
fanOutDict.updateValue(messageDict, forKey: messageIdPath)
fanOutDict.updateValue(messageIdDict, forKey: fromIdPath)
fanOutDict.updateValue(messageIdDict, forKey: toIdPath)
let rootRef = Database.database().reference()
rootRef?.updateChildValues(fanOutDict)
}
The problem wasn't a new key was not getting generated. #FrankvanPuffelen pointed out in th comments that a new key should get generated every time which is exactly what was happening.
The problem was the fanout was overwriting what was originally written at these 2 paths:
let fromIdPath = "user-messages/\(currentUserId)"
let toIdPath = "user-messages/\(toId)"
It appeared the key was the same because the data kept getting overwritten.
The way I was generating the key works fine
I am working with a Firebase Real Time database and I am having troubles with the execution of code at specific times. When I ask the database if there is a specific value in it, it executes the code to retrieve the data but then automatically continues unto the next line, not waiting for the retrieval of data. I am using this code to retrieve the data:
self.ref.child("Period \(periodListValue)").child("Students").child("\(studentName)").child("Novel Author").observeSingleEvent(of: .value) { (snapshot) in
self.CurrentAuthorTextField.text = (snapshot.value as! String)
}
The line of code right below this that is not associated with the database, executes right after this code above executes. Meaning I can't use any of the database information of the code right below the one shown above.
I am trying to explain this as best as I.
Any help?
Well, you have to use the completion handler for the following:-
func ifStudentPresent(studentName: String, completionHandler: #escaping ((_ exist : Bool) -> Void))
{
self.ref.child("Period \(periodListValue)").child("Students").child("\ .
(studentName)").child(studentName).observeSingleEvent(of: .value) { (snapshot) in
if snapshot.exists(){
completionHandler(true)
}else{
print("Student Don't exist")
completionHandler(false)
}
})
}
The reason you might be going through this problem is related to invalid database security rules. These can easily prevent you from retrieving your desired data and synchronizing your realtime database.
Let's assume you are trying to synchronize the ref database reference. You need to set the correct rules that allow reading from this database reference - something along the lines of ".read" = true".
[Warning] Please be careful with these database security rules. Incorrect rules can lead to drastically undesired behaviors, such as people illegally reading and/or writing from/into your database. A good video on how to set flawless security rules is The key to firebase security - Google I/O 2016
let dispatch = DispatchGroup.init()
dispatch.enter()
self.ref.child("Period \(periodListValue)").child("Students").child("\(studentName)").child("Novel Author").observeSingleEvent(of: .value) { (snapshot)
in
self.CurrentAuthorTextField.text = (snapshot.value as! String)
dispatch.leave()
}
dispatch.notify(queue: .main) {
//write code here, it will execute after database fetch
}
I have a query running to check .childAdded at a location in my database.
It works well when data is found, however, if there is not data at the location, it can't fire the query and therefore this does not allow me to use snapshot.exists because it doesn't even run the query.
This is my current code
let favouriteRef = self.databaseRef.child("users").child(userID!).child("Favourites")
// Code doesn't run past this line when no data at location
favouriteRef.queryOrderedByKey().observe(.childAdded, with: { (snapshot) in
let favouriteID = "\(snapshot.value!)"
let usersRef = self.databaseRef.child("users")
usersRef.observeSingleEvent(of: .value, with: { (users) in
for user in users.children {
let favCleaner = UserClass(snapshot: user as! DataSnapshot)
if favouriteID == favCleaner.uid {
tempFav.append(favCleaner)
}
}
self.hasFavourites = true
self.tableView.reloadData()
self.usersArray = tempFav
self.collectionView.reloadData()
})
})
I would like to find a way to receive a callback if the query doesn't run (no data at location)
Thanks.
If there is absolutely no data at the location, then obviously this event trigger is not sufficient for you to get the data because this event only gets triggered when something gets added.
So you have two options
Add another trigger of type .observeSingleEvent(of: .value, with: { (snapshot) in
// Get the values and write the relevant actions
}
Or you can update this event to type .observe(.value, with: {snapshot in // write the relevant code
}
Both approaches have their advantage and disadvantage.
First approach will need you to write more code while minimising the number of triggers from your database to your UI. In second approach, there will be more triggers to the UI but it can be fairly easy to code.
From what I can see, you are first trying to establish whether data exists in the favorite node of your database and then comparing it to another snapshot. So if the number of delete or update events are relatively small, my suggestion is to go for approach two.
How do I retrieve a value (other than username and user id, which seem easier to get) for the current user from the database.
Ironically, I can set the value as follows and that works just fine:
let databaseRef = FIRDatabase.database().reference()
userID = (FIRAuth.auth()?.currentUser?.uid)! as String
databaseRef.child("users").child(userID!).child("TermCond").setValue("Yes")
But for the life of me I cannot work out what to put instead of setValue if I simply want to retrieve the current TermCond value. I thought just using value as for example in
let DesiredValue = databaseRef.child("users").child(userID!).child("TermCond").value as? String
Would suffice, but nothing works. I am confused why retrieving the value should be more difficult than setting it.
To "read" a value from Firebase, you need to add a reference listener that gets called every time that value changes.
In your case, that could be something like:
let databaseRef = FIRDatabase.database().reference()
databaseRef.child("users").child(userID!).child("TermCond").observe(FIRDataEventType.value, with: { (snapshot) in
let desiredValue = snapshot.value as? String
})
This block of code will get triggered every time your value changes. If you only want to read it once, you can use observeSingleEvent:of:with instead of observe:with.
This is as described in the Firebase documentation: https://firebase.google.com/docs/database/ios/read-and-write
I recommend you read their entire Documentation to get an idea of how Firebase works, as it is very different from traditional databases.
I can also recommend the following tutorial if you'd like to learn a bit more about the Firebase Database and how it works: https://www.raywenderlich.com/139322/firebase-tutorial-getting-started-2
I've solved this now (based on Aleksander's reply). The way I did it is as follows.
databaseRef.child("users").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
self.desiredValue = value?["TermCond"] as? String ?? ""
self.LabelToShow.text = self.desiredValue!
}) { (error) in
print(error.localizedDescription)
}
This works absolutely fine and shows the value of TermCond in the LabelToShow on my iOS screen.