Im trying to retrieve an address I have stored in a Map object within Firebase.
But I can't seem to retrieve any data, When I print out the result it doesn't display anything.
Here is my Firebase Structure
This is the request I'm making to Firebase
let key = UserDefaults.standard.value(forKey: "uid") as? String ?? "Null"
let docRef = firebaseDB.collection("user").document(key)
docRef.getDocument { (document, error) in
if let document = document, document.exists {
let docData = document.data()
let city = docData!["city"] as! String
let country = docData!["country"] as! String
let county = docData!["county"] as! String
let lineOne = docData!["lineOne"] as! String
let lineTwo = docData!["lineTwo"] as! String
let postCode = docData!["postCode"] as! String
print(city,country,county,lineOne,lineTwo,postCode)
} else {
print("Document does not exist")
}
If this is crashing
let city = docData!["city"] as! String
it indicates a node does not contain a child of 'city'. Perhaps it's missing entirely or is City instead of city.
Force unwrapping a var (e.g. as!) which could potentially be nil is essentially stating 'Hey var, you will never be nil' and can lead to app crashes and instability.
A better way to handle this and protect your code is to properly handle data in the cases where it may not be what is expected.
A better method is to use nil coalescing like this, which provides a default value if city is nil
let city = data!["city"] as? String ?? "no city selected"
or if you want to work with nil then change the way you're reading the child nodes to
let city = document.get("city")
Keeping in mind that while this code won't crash, city could be nil in this situation so you need to handle that accordingly in the code following that statement.
You can also use if let statements
var aPlace = PlaceStruct()
if let city = document.get("city") as? String {
aPlace.city = city
} else {
aPlace.city = "Hometown"
}
or guard statements to protect your data.
Whatever the situation, don't force unwrap potentially nil vars unless you know they will never be nil - handle those vars that can be nil gracefully.
Related
I've got a code which normally should return to me a value from Firebase.
My Firebase struct is :
Experience{
UserId{
LDG_DAY: "4"
LDG_NIGHT: "0"
APCH_IFR: "0"
}
}
My code is :
func getUserExp(){
let ref = Database.database().reference()
let userID = Auth.auth().currentUser?.uid
let Date = self.flightDate.text
ref.child("Experience")/*.child(userID!)*/.observeSingleEvent(of: .value) {(snapshot) in
if snapshot.hasChild(userID!){
let value = snapshot.value as? NSDictionary
let ldg_day = value?["LDG_DAY"] as? String ?? "123"
let ldg_night = value?["LDG_NIGHT"] as? String ?? "0"
let apch_ifr = value?["APCH_IFR"] as? String ?? "0"
self.intLdgDay = Int(ldg_day)!
self.intLdgNight = Int(ldg_night)!
self.intApchIfr = Int(apch_ifr)!
print("string = \(ldg_day) int = \(self.intLdgDay)")
}
}
}
Now the code didn't work as I would like... In fact my code return the basic as? String ?? "123" value but the snapshot.value get the good value from firebase ...
What's wrong ? I use this code for many other part of my app and no problems about it ?
Thanks for your help
I believe you want to ensure the node exists before trying to read the child data.
NOTE:
I see the path to read has the uid commented out so it's unclear if you intended to read a single user (leaving in the uid) or if you actually wanted to load every user at one time (thousands). This answer assumes you are intending to read that specific user node only. See #Callam answer if you intended to read ALL of the users nodes at one time.
The code you have now is using snapshot.hasChild which looks within the node to see if the child, the users uid exists, and it doesn't so the code will always fail.
if snapshot.hasChild(userID!)
I think what you want to do is use snapshot.exists to ensure it's a valid node before reading. Here's the code:
let experienceRef = self.ref.child("Experience")
let usersExpRef = experienceRef.child(uid)
usersExpRef.observeSingleEvent(of: .value) { snapshot in
if snapshot.exists() {
let value = snapshot.value as! [String: Any]
let ldg_day = value["LDG_DAY"] as? String ?? "123"
print("string = \(ldg_day)")
} else {
print("the \(uid) node does not exist")
}
}
I would also suggest safely unwrapping options before attempting to work with them as they could be nil, and that would crash your code.
guard let thisUser = Auth.auth().currentUser else { return }
let uid = thisUser.uid
Note I also replaced the old objc NSDictionary with it's Swifty counterpart [String: Any]
Assuming your struct is from the root, and Experience contains more than one user ID, your code is currently observing the value for all user IDs since the /*.child(userID!)*/ is commented out.
Therefore you are requesting every user's experience and checking on the client if the current user exists as a child – this will succeed if the current user's ID is present at Experience/$uid.
ref.child("Experience")/*.child(userID!)*/.observeSingleEvent(of: .value) { (snapshot) in
if snapshot.hasChild(userID!) {
let value = snapshot.value as? NSDictionary
Now we have a snapshot with all Experiences and we've confirmed that it has a child for the current user's ID – we would need to get that child and cast the value of that to a dictionary.
let value = snapshot.childSnapshot(forPath: userID).value as? NSDictionary
This fixes the issue but obviously, we don't want to download every experience on a single user's device, and they maybe shouldn't even have the permission to request that reference location either.
So if you uncomment .child(userID!), the snapshot will be of just one Experience, so snapshot.hasChild(userID!) will fail. Instead, you can use snapshot.exists() and/or a conditional cast to determine if the snapshot for the userID is existent and/or thereby castable.
func getUserExp() {
let ref = Database.database().reference()
let userID = Auth.auth().currentUser?.uid
let Date = self.flightDate.text
ref.child("Experience").child(userID!).observeSingleEvent(of: .value) { snapshot in
if snapshot.exists() {
let value = snapshot.value as? [String:String]
let ldg_day = value?["LDG_DAY"] ?? "123"
let ldg_night = value?["LDG_NIGHT"] ?? "0"
let apch_ifr = value?["APCH_IFR"] ?? "0"
self?.intLdgDay = Int(ldg_day)!
self?.intLdgNight = Int(ldg_night)!
self?.intApchIfr = Int(apch_ifr)!
print("string = \(ldg_day) int = \(self.intLdgDay)")
} else {
print("experience for \(snapshot.key) doesn't exist")
}
}
}
You can clean this up a bit with a struct and extension.
// Experience.swift
struct Experience {
var ldg_day: String
var ldg_night: String
var apch_ifr: String
}
extension Experience {
static var currentUserRef: DatabaseReference? {
return Auth.auth().currentUser.flatMap {
return Database.database().reference(withPath: "Experience/\($0.uid)")
}
}
init?(snapshot: DataSnapshot) {
guard snapshot.exists() else { return nil }
let value = snapshot.value as? [String:String]
self.ldg_day = value?["LDG_DAY"] ?? "123"
self.ldg_night = value?["LDG_NIGHT"] ?? "0"
self.apch_ifr = value?["APCH_IFR"] ?? "0"
}
}
Et voilà,
func getUserExp() {
Experience.currentUserRef?.observeSingleEvent(of: .value, with: { [weak self] in
if let experience = Experience(snapshot: $0) {
self?.intLdgDay = Int(experience.ldg_day)!
self?.intLdgNight = Int(experience.ldg_night)!
self?.intApchIfr = Int(experience.apch_ifr)!
print("string = \(experience.ldg_day) int = \(self.intLdgDay)")
} else {
print("experience for \($0.key) doesn't exist")
}
})
}
Im successfully getting data from Firebase but I can't manage to push it into array to use. My database is as follows:
users
-Wc1EtcYzZSMPCtWZ8wRb8RzNXqg2
-email : "mike#gmail.com"
-lists
-LJiezOzfDrqmd-hnoH-
-owner: Wc1EtcYzZSMPCtWZ8wRb8RzNXqg2
-LJif-UgPgbdGSHYgjY6
-owner: Wc1EtcYzZSMPCtWZ8wRb8RzNXqg2
shopping-lists
-LJh6sdBJtBCM7DwxPRy
-name: "weekly shopping"
-owner: "mike#gmail.com"
I have a home page after login that shows existing shopping lists on table if they exist. On viewDidLoad() I get shopping list IDs from the user and use those IDs as a reference to get details from shopping-lists.
However, I cant manage to save these data into an array as it gets deleted after closure. How can I do that in a clean way?
override func viewDidLoad() {
super.viewDidLoad()
SVProgressHUD.show()
tableView.allowsMultipleSelectionDuringEditing = false
// Sets user variable - must have
Auth.auth().addStateDidChangeListener { auth, user in
guard let user = user else { return }
self.user = User(authData: user)
// If new user, write into Firebase
self.usersRef.observeSingleEvent(of: .value, with: { snapshot in
if !snapshot.hasChild(self.user.uid) {
self.usersRef.child(user.uid).setValue(["email": user.email!])
}
})
// Get shopping lists data from "users/lists"
self.usersRef.child(user.uid).child("lists").observe(.value, with: { snapshot in
// Get list IDs
if snapshot.exists() {
if let result = snapshot.children.allObjects as? [DataSnapshot] {
for child in result {
self.listNames.append(child.key)
}
}
}
// Use list IDs - to get details
for item in self.listNames {
let itemRef = self.shoppingListsRef.child(item)
itemRef.observeSingleEvent(of: .childAdded, with: { (snapshot) in
if let value = snapshot.value as? [String: Any] {
let name = value["name"] as? String ?? ""
let owner = value["owner"] as? String ?? ""
let shoppingList = ShoppingList(name: name, owner: owner)
self.items.append(shoppingList)
}
})
}
})
self.tableView.reloadData()
SVProgressHUD.dismiss()
}
}
(the question is a bit unclear so several parts to this answer to cover all possibilities. This is Swift 4, Firebase 4/5)
You don't really need to query here since you know which nodes you want by their key and they will always be read in the in order of your listNames array. This assumes self.listNames are the keys you want to read in.
for item in listNames {
let itemRef = shoppingListsRef.child(item)
itemRef.observe(.value, with: { (snapshot) in
if let value = snapshot.value as? [String: Any] {
let name = value["name"] as? String ?? ""
let owner = value["owner"] as? String ?? ""
print(name, owner)
}
})
}
Generally, queries are used when you are searching for something within a node - for example if you were looking for the node that contained a child name of 'weekly shopping'. Other than that, stick with just reading the nodes directly as it's faster and has less overhead. Keep reading...
I also removed the older NSDictionary and went with the Swift [String: Any] and modified your error checking
However, the real issue is reading that node with an .observe by .value. Remember that .value reads in all children of the node and then the children need to be iterated over to get each separate DataSnapshot. Also, .observe leaves an observer on the node notifying the app of changes, which I don't think you want. So this will answer the question as posted, (and needs better error checking)
for item in listNames {
let queryRef = shoppingListsRef
.queryOrdered(byChild: "name")
.queryEqual(toValue: item)
queryRef.observe(.value, with: { (snapshot) in
for child in snapshot.children { //even though there is only 1 child
let snap = child as! DataSnapshot
let dict = snap.value as! [String: Any]
let name = dict["name"] as? String ?? ""
let owner = dict["owner"] as? String ?? ""
print(name, owner)
}
})
}
And the answer...
This is probably more what you want...
for item in listNames {
let queryRef = shoppingListsRef
.queryOrdered(byChild: "name")
.queryEqual(toValue: item)
queryRef.observeSingleEvent(of: .childAdded, with: { snapshot in
let dict = snapshot.value as! [String: Any]
let name = dict["name"] as? String ?? ""
let owner = dict["owner"] as? String ?? ""
print(name, owner)
})
}
note the .childAdded instead of .value which presents the snapshot as a single DataSnapshot and doesn't need to be iterated over and the .observeSingleEvent which does not leave an observer attached to each node.
Edit
Based on additonal information, it would be best too change the structure to this
shopping-lists
-LJh6sdBJtBCM7DwxPRy
-name: "weekly shopping"
-uid: "Wc1EtcYzZSMPCtWZ8wRb8RzNXqg2"
and then when the user logs in just query the shopping lists node for any uid that's theirs.
` let query = ref?.child("Reviews").queryOrdered(byChild: "UserID").queryEqual(toValue: myUser.userId)
query?.observeSingleEvent(of: .value) { snapshot in
for child in snapshot.children {
let snap = child as! DataSnapshot
let dict = snap.value as! [String: Any]
let uid = dict["UserID"] as! String
let review = dict["Body"] as! String
let rating = dict["Rating"] as! String
let titleID = dict["TitleID"] as! String
let reviewID = dict["ReviewID"] as! String
let ratingID = dict["RatingID"] as! String
`
THE ERROR OCCURS AT THE ratingID call to the database. It unwraps nil.
I am trying to adapt a pre existing Firebase database with a new key/value.
I then try to display entries in my tableview and I get a crash with unwrap returning nil. I know why this is happening and it's because the previous data does not have the new key/value I want to include in the node going forward. I have tried many different things such as if let and guard let without much fortune. How do I add new key/Values and still have the tableview read entries that don't have the new value?
I include an image of the current node and I want to add a 'RatingsID' to the node. When I do, I get the unwrap nil error.
Database node prior to new key/value
Your code is super close, just need to protect the code in case the ratingID key doesn't exist.
So change
let ratingID = dict["RatingID"] as! String
to
let ratingID = dict["RatingID"] as! String ?? ""
So if the RatingID node does not exist, you'll set ratingID to an empty string (or whatever string you want)
You could also code it to only operate on the value of that key if the node exists (not nil)
if let someVal = dict["xxx"] {
//do something with someVal
} else {
print("xxx node wasn't found")
}
Here's a complete example: We are reading some messages from the messages node and some of them have a test_key node and some dont. For those that don't, default string is assigned to test
let postsRef = self.ref.child("messages")
postsRef.observe(.childAdded) { snapshot in
let dict = snapshot.value as! [String: Any]
let msg = dict["msg"] as! String
let test = dict["test_key"] ?? "default string"
print(msg, test)
}
Having a hard time figuring out how to iterate through the my messages database so I can find a key that matches a user's phone number... this method crashes and all the other ways I've tried fail as well. I could really use the help thanks.
func retrieveMessages(){
let messagesDB = Database.database().reference().child("iMessenger/Messages")
messagesDB.observe(.childAdded, with: {(snapshot) in
let snapshotValue = snapshot.value as! Dictionary<String, String>
//This conditional is suppose to filter out messages that aren't to or from the user
if snapshotValue["sender"]! == userPhoneNumber || snapshotValue["receiver"]! == userPhoneNumber{
let text = snapshotValue["messageBody"]!
let sender = snapshotValue["sender"]!
let message = Message()
message.messageBody = text
message.sender = sender
self.messageArr.append(message)
self.configureTableView()
self.messagesTableView.reloadData()
self.scrollToLastRow()}}
)}
You should not use ! in your code as much as possible, it is bound to crash if the value is nil and I think you need to downcast the value to String to compare the phone numbers, so you can modify your code as follows: (use optional binding and downcasting)
if let snapshotValue = snapshot.value as? [String: Any], let senderNumber = snapshotValue["sender"] as? String,let receiverNumber = snapshotValue["receiver"] as? String {
//now you should compare these values as follows...
if senderNumber == userPhoneNumber || receiverNumber == userPhoneNumber {
//do your stuff...
}
}
Everything works swimmingly except for when I do a random string like "fds", how would I correctly and efficiently use a guard to protect from this sort of error?
init(weatherData: [String: AnyObject]) {
city = weatherData["name"] as! String
let weatherDict = weatherData["weather"]![0] as! [String: AnyObject]
description = weatherDict["description"] as! String
icon = weatherDict["icon"] as! String
let mainDict = weatherData["main"] as! [String: AnyObject]
currentTemp = mainDict["temp"] as! Double
humidity = mainDict["humidity"] as! Int
let windDict = weatherData["wind"] as! [String: AnyObject]
windSpeed = windDict["speed"] as! Double
}
how would I correctly and efficiently use a guard to protect from this sort of error?
Why would you want to? If the caller does not hand you a dictionary whose "name" key is present and is a string, you are dead in the water because you cannot initialize city. You want to crash.
If you would like to escape from this situation without actually crashing, then make this a failable initializer and fail (return nil) if the dictionary doesn't contain the needed data. This effectively pushes the danger of crashing onto the caller, because the result will be an Optional that might be nil, and the caller must check for that.
init?(weatherData: [String: AnyObject]) {
guard let city = weatherData["name"] as? String else {return nil}
self.city = city
// ... and so on ...
}
But what I would do is none of those things. I would rewrite the initializer as init(city:description:icon:currentTemp:humidity:windSpeed:) and force the caller to parse the dictionary into the needed data. That way, if the data is not there, we don't even try to initialize this class in the first place. My argument would be that it is the caller's job to parse the dictionary; this class should have no knowledge of the structure of some complex dictionary pulled off the Internet (or whatever the source is).