I'm having an issue with getting dispatchgroup functions to work when combined with multiple for loops. In my code below, my first dispatch pulls in the coauthorId field for each of the coauthorID under my userId.
I'm getting an error when the code reaches the first dispatchgroup.leave() function so I'm not sure if it has something to do with where the dispatchgroup functions are placed.
Datebase structure:
posts
--ABC //my userId
--XXX //coauthorId
--coauthorId: XXX
--ZZZ //coauthorId
--coauthorId: ZZZ
--YYY //coauthorId
--coauthorId: YYY
Code:
var ListA = [String]()
var ListB = [String]()
func fetchPosts() {
let dispatchGroup = DispatchGroup()
let currentUser = Auth.auth().currentUser!
dispatchGroup.enter()
Database.database().reference().child("posts").child(currentUser.uid).observeSingleEvent(of: .value, with: { (snapshot : DataSnapshot) in
// Iterate through all the children:
for child in snapshot.children.allObjects as! [DataSnapshot] {
let value = child.value as? NSDictionary
let coauthorId = value?["coauthorId"] as? String ?? ""
Database.database().reference().child("posts").child(coauthorId).observeSingleEvent(of: .value, with: { (snapshot : DataSnapshot) in
// Iterate through all the children:
for child1 in snapshot.children.allObjects as! [DataSnapshot] {
let value1 = child1.value as? NSDictionary
let coauthorId1 = value1?["coauthorId"] as? String ?? ""
self.ListA.append(coauthorId1)
dispatchGroup.leave() //this is where I get an error
}
})
}
})
dispatchGroup.enter()
//fetches the Id of my posts
Database.database().reference().child("posts").child(currentUser.uid).observeSingleEvent(of: .value, with: { (snapshot : DataSnapshot) in
// Iterate through all the children:
for child in snapshot.children.allObjects as! [DataSnapshot] {
// Add the user ID to the array:
let value = child.value as? NSDictionary
let mycoauthorId = value?["coauthorId"] as? String ?? ""
self.ListB.append(mycoauthorId)
}
dispatchGroup.leave()
})
// Notify the dispatch group:
dispatchGroup.notify(queue: DispatchQueue.main, execute: {
// Now that both completion blocks (from your two observers) ran, combine both arrays
let combinedArray = self.ListA + self.ListB
print(combinedArray)
})
Related
Basically everything is working, except the showChild func is returning completion([]) because of the guard catData = Category(snapshot: catInfo). I am wondering why the guard let is returning completion. When I debug, catInfo does have 1 value as shown in my pic of database and I want to append catData.main to "cats". Below is code for the service method and Category model as well.
Firebase Database
static func showChild(completion: #escaping ([String]) -> Void) {
let ref = Database.database().reference().child("category").child(User.current.uid)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
guard let snapshot = snapshot.children.allObjects as? [DataSnapshot] else {
return completion([])
}
var cats = [String]()
for catInfo in snapshot {
guard let catData = Category(snapshot: catInfo) else {
return completion([])
}
cats += catData.main
}
completion(cats)
})
}
import Foundation
import FirebaseDatabase.FIRDataSnapshot
class Category {
var key: String?
let main: [String]
init?(snapshot: DataSnapshot) {
guard !snapshot.key.isEmpty else {return nil}
if let dict = snapshot.value as? [String : Any]{
let main = dict["main"] as? [String]
self.key = snapshot.key
self.main = main ?? [""]
}
else{
return nil
}
}
}
The issue is pretty straightforward.
While your snapshot contains at least one node of data, it's not in a format that the Category init method understands. You're iterating over it's child nodes and in your screenshot, there's only one, with a key of 'main'
You are observing this node
fb_root
category
2ayHe...
and then you're iterating over it's child nodes which will be
main
0: Performance
so the key is 'main' and it's value is '0: Performance'
but your Category class is looking for a child node of 'main'
let main = dict["main"] as? [String]
There's not enough info to understand what will be contained in the rest of the structure so I can't tell you how to correct it, but at least you know what the problem is.
To clarify, this line
if let dict = snapshot.value as? [String : Any]
will make dict = [0: "Performance]
firebase structure
In the firebase structure you can see i have to delete specific user (currentUserId) in all the groups:
it's what i try to do:
###########################UPDATED###################################
let groupsRef = self.root.child("groups")
groupsRef.observeSingleEvent(of: .value, with: { snapshot in
for groupChild in snapshot.children {
let groupSnap = groupChild as! DataSnapshot
var dict = groupSnap.value as! [String: Any]
let uid = dict["utenti"] as! [String: Bool]
for each in uid {
if each.key == self.currentUserID{
print(each.key)
//i now need a way to remove this key:value
}
}
}
})
I'm new so i'm not able to go further in extracting every key of ditcionary, than i will compare to the one i have to delete and if it's the same i will delete.
Can someone help?
let groupsRef = self.root.child("groups")
groupsRef.observeSingleEvent(of: .value, with: { snapshot in
for groupChild in snapshot.children {
let groupSnap = groupChild as! DataSnapshot
let groupKey = groupSnap.key
//added a groupKey to track the id of each group
var dict = groupSnap.value as! [String: Any]
var uid = dict["utenti"] as! [String: Bool]
//then for each key:value in uid check if is there a key = to currentuserID
for each in uid {
if each.key == self.currentUserID{
uid.removeValue(forKey: each.key)
//here you remove currentuserId from the dictionary and below
//finally you set back the new value of the dictionary without currentuserId
self.root.child("groups").child(groupKey).child("utenti").setValue(uid)
}
}
}
})
you can use
for (key, value) in uid {
}
to loop over a dictionary.
But really, looking in the official documentation of swift would give you the right answer...
let groupsRef = self.root.child("groups")
groupsRef.observeSingleEvent(of: .value, with: { snapshot in
for groupChild in snapshot.children {
let groupSnap = groupChild as! DataSnapshot
for subGroupChild in groupSnap.children {
//Here you need to remove that specific user if condition match
//specificUserUID is that user's id that user to be deleted
if let snapref = subGroupSnap as! DatabaseReference {
snapref.queryOrdered(byChild: "utenti").queryEqual(toValue: specificUserUID).observe(.childAdded, with: { (snapshot) in
snapshot.removeValue(completionBlock: { (error, reference) in
if error != nil {
print("There has been an error:\(error)")
}
})
})
}
}
}
})
Your code will go like above you just need find thaat user by user ID and delete that particular snapshot.
Hi there i'm newest in swift. I am working with a firebase database with at 2 layer of hierarchy as well as many children for each node. I got 1st layer (descript, enddata and other), but i stll can't get the news node. Is in 3 to 5 random keys. I sow many issues but still not have issue for me.
I'm understand i'm doing some wrong but what?
The Firebase is:
i need retreat the news child
struct is
struct ICONews {
let ICOId: String
let news1: String
let news2: String
let news3: String
init?(ICOId: String, dict: [String: Any] ) {
self.ICOId=ICOId
guard let news1 = dict[""] as? String,
let news2 = dict[""] as? String,
let news3 = dict[""] as? String
else { return nil }
self.news1 = news1
self.news2 = news2
self.news3 = news3
}
}
struct NewsSnapShot {
let posts: [ICONews]
init?(with snapshot: DataSnapshot) {
var posts = [ICONews] ()
guard let snapDict = snapshot.value as? [String: [String: Any]] else { return nil }
for snap in snapDict {
guard let post = ICONews (ICOId: snap.key, dict: snap.value) else {continue}
posts.append(post)
}
self.posts=posts
}
}
class of DataBase
class DatabaseService {
static let shared = DatabaseService()
private init(){}
let ICOReference = Database.database().reference()
}
and retreat method
DatabaseService.shared.ICOReference.child("news").observe(DataEventType.value, with: { (snapshot) in
guard let postsSnapShot = ICOSnapShot(with: snapshot) else {return}
})
done
Database.database().reference().observeSingleEvent(of: .value, with: {(snapshot) in
let enumerator = snapshot.children
while let rest = enumerator.nextObject() as? DataSnapshot {
let values = (rest as! DataSnapshot).value as? NSDictionary
let enumeratorMap1 = (rest as! DataSnapshot).children
while let rest2 = enumeratorMap1.nextObject() as? DataSnapshot {
let valuesMap1 = (rest2 as! DataSnapshot).value as? NSDictionary
if (rest2 as! DataSnapshot).key == "news" {
print(rest2.value)
}
}
}
})
Make the the Firebase Api call like
Database.database().reference().child("users").child(userID).observe(.childAdded, with: { (snapshot) in
if snapshot.exists() {
let receivedMessage = snapshot.value as! [String: Any]
let name = receivedMessage["name"] as? String ?? ""
let id = receivedMessage["id"] as? Double ?? 0.0
let profileurl = receivedMessage["url"] as? String ?? ""
completion(User(name: name, id: id, url: url))
} else {
failure()
}
})
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.
}
I have this code below in order to retrieve a list of restaurants and their data. However, it's not storing the data, and every time I try to return the array it returns nil. But if I print it, prints the data. Any suggestions?
func getRestaurants()-> Array<Restaurant>{
var baruri = [Restaurant]()
dataBaseRef.child("AthensRestaurants/Restaurants").observe(.value, with: { (snapshot) in
if let snapshot = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshot {
print(snap)
if let restaurantData = snap.value as? Dictionary<String, AnyObject> {
let restaurant = Restaurant(restaurantData: restaurantData)
baruri.append(restaurant)
print(baruri)
}
}
}
})
return baruri
}
The firebase observe is an asynchronous callback function, so it will run after it is finished. In other words, your return baruri will always runs before the value got back. You can use completion handler to get the value you want.
var restaurants = [Restaurant]()
func getRestaurants(completion: #escaping (Array<Restaurant>) -> Void){
var baruri = [Restaurant]()
dataBaseRef.child("AthensRestaurants/Restaurants").observe(.value, with: { (snapshot) in
if let snapshot = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshot {
print(snap)
if let restaurantData = snap.value as? Dictionary<String, AnyObject> {
let restaurant = Restaurant(restaurantData: restaurantData)
baruri.append(restaurant)
print(baruri)
completion(baruri)
}
}
}
})
}
// Call this function with call back
getRestaurants { restaurants in
self.restaurants = restaurants
}