This is how my Firebase database looks like:
I want to get the names "Attack on Nibeiwa", "Fort Capuzzo" and so on instead of the rest of the things. My current code gives my the complete JSON:
let ref = Database.database().reference().child("Battle Details")
ref.observeSingleEvent(of: .value, with: { (snap : DataSnapshot) in
print("\(String(describing: snap.value))")
}) { (err: Error) in
print("\(err.localizedDescription)")
}
To retrieve the names try the following:
let ref = Database.database().reference().child("Battle Details")
ref.observeSingleEvent(of: .value, with: { (snap : DataSnapshot) in
for child in snap.children {
let key = (child as AnyObject).key as String
}
}) { (err: Error) in
print("\(err.localizedDescription)")
}
Here the snapshot is at Battle Details then you iterate inside the direct children which are the names in this case and retrieve the names using child.key
Related
I'm trying to get the old value of a field when it is changed in Firestore. Is there any way to access what the previous value of a field is after it is changed? Here is my current code, I want to access the old nickName under .modified and print out what the new nickName is and also the old one.
db.collection("cities").whereField("state", isEqualTo: "CA").addSnapshotListener { querySnapshot, error in
guard let snapshot = querySnapshot else {
print("Error fetching snapshots: \(error!)")
return
}
snapshot.documentChanges.forEach { diff in
if (diff.type == .added) {
print("New city: \(diff.document.data())")
let nickName = myData["nickName"] as? String ?? ""
}
if (diff.type == .modified) {
let nickName = myData["nickName"] as? String ?? ""
}
if (diff.type == .removed) {
let nickName = myData["nickName"] as? String ?? ""
}
}
}
Unfortunately, that is not a feature of Firestore. What you can do is have another field oldNickName and using Firebase Functions, automatically update that when the nickName field is changed.
The best solution is storing nickName locally, so you can refer back to your local variable when nickName changes, accessing the newly updated one in the database and the previous nickName locally. Here is the updated code:
var nickNames = [String : String]()
db.collection("cities").whereField("state", isEqualTo: "CA").addSnapshotListener { snapshot, error in
guard error == nil, let snapshot = snapshot?.documentChanges else { return }
snapshot.forEach {
let document = $0.document
let documentID = document.documentID
let nickName = document.get("nickName") as? String ?? "Error"
switch $0.type {
case .added:
print("New city: \(document.data())")
nickNames[documentID] = nickName
case .modified:
print("Nickname changed from \(nickNames[documentID]) to \(nickName)")
nickNames[documentID] = nickName
case .removed:
print("City removed with nickname \(nickNames[documentID])")
nickNames.removeValue(forKey: documentID)
}
}
}
nickNames is a dictionary with key cityID and value nickName. This code is written in Swift 5.
I'm trying to paginate posts that users are following to my collection view from my firebase database. Currently only 4 posts are being appended to the collection view and not loading anymore when I scroll down.
I've tried changing the number of posts loaded initially with no luck.
fileprivate func fetchFollowingUserIds() {
guard let uid = Auth.auth().currentUser?.uid else { return }
Database.database().reference().child("user-following").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
guard let userIdsDictionary = snapshot.value as? [String: Any] else { return }
userIdsDictionary.forEach({ (key, value) in
Database.fetchUserWithUID(uid: key, completion: { (user) in
self.fetchPostsWithUser(user: user)
})
})
}) { (err) in
print("Failed to fetch following user ids:", err)
}
}
var posts = [Post]()
fileprivate func fetchPosts() {
guard let uid = Auth.auth().currentUser?.uid else { return }
Database.fetchUserWithUID(uid: uid) { (user) in
self.fetchPostsWithUser(user: user)
}
}
var isFinishedPaging = false
fileprivate func fetchPostsWithUser(user: User) {
self.collectionView?.refreshControl?.endRefreshing()
let ref = Database.database().reference().child("posts").child(user.uid)
var query = ref.queryOrdered(byChild: "creationDate")
if posts.count > 0 {
let value = posts.last?.creationDate.timeIntervalSince1970
query = query.queryEnding(atValue: value)
}
query.queryLimited(toLast: 4).observeSingleEvent(of: .value, with: { (snapshot) in
guard var allObjects = snapshot.children.allObjects as? [DataSnapshot] else { return }
allObjects.reverse()
if allObjects.count < 4 {
self.isFinishedPaging = true
} else {
self.isFinishedPaging = false
}
if self.posts.count > 0 && allObjects.count > 0 {
allObjects.removeFirst()
}
allObjects.forEach({ (snapshot) in
guard let dictionary = snapshot.value as? [String: Any] else { return }
var post = Post(user: user, dictionary: dictionary)
post.id = snapshot.key
self.posts.append(post)
})
self.collectionView?.reloadData()
}) { (err) in
print(err)
}
}
I simply want it to load more posts when the user scrolls down.
There may be a query issue or a potential logic issue. Lets assume you want to present posts to the user, with the most recent at the top of the list and allow the user to scroll down to see earlier posts.
Let's address both with an example:
We don't have your structure but keeping it super simple, suppose your posts have the following structure with creation dates
post_0
creation_date: "20180101"
post_1
creation_date: "20180102"
post_2
creation_date: "20180103"
post_3
creation_date: "20180104"
post_4
creation_date: "20180105"
post_5
creation_date: "20180106"
post_6
creation_date: "20180107"
post_7
creation_date: "20180108"
Here's your initial query, order by creation date, which will load the last 4 posts from the 5th to the 8th
var query = ref.queryOrdered(byChild: "creationDate")
Then subsequent queries are ordered by creation date but the ending value is not the creation date but the time elapsed since 1970 of the creation date.
let value = posts.last?.creationDate.timeIntervalSince1970
var query = ref.queryOrdered(byChild: "creationDate").queryEnding(atValue: value)
I would guess you just want to load the next 4 earlier posts. So as this sit in the array, they look like this:
20180108
20180107
20180106
20180105
One way to do that is the get the creationDate of the last post from your dataSource (which will be the oldest post)
20180105
Then query by creationDate, endingAt the creation date of the last post, getting 5 total posts, then remove the last one
20180101
20180102
20180103
20180104
20180105
then reversed
20180105
20180104
20180103
20180102
20180101
and remove the first
20180104
20180103
20180102
20180101
something like this
let lastD = self.postsArray.last
self.postsArray = []
let postsRef = self.ref.child("posts")
let queryRef = postsRef.queryOrdered(byChild: "creation_date")
let queryEndingRef = queryRef.queryEnding(atValue: lastD)
let queryLimitedRef = queryEndingRef.queryLimited(toLast: 5)
queryLimitedRef.observeSingleEvent(of: .value, with: { snapshot in
guard var thisArray = snapshot.children.allObjects as? [DataSnapshot] else { return }
thisArray.reverse()
thisArray.removeFirst()
for post in thisArray {
let theDate = post.childSnapshot(forPath: "creation_date").value as! String
self.postsArray.append(theDate)
}
})
I want to be able to list users in a tableview by fetching their UID Value from a key stored in my database. As of now, the code only fetches the first value in the database rather than all of the values. Here is the code for fetching the applicants.
func loadApplicants() {
let usersRef = ref.child("users")
usersRef.observe(.value, with: { (users) in
var resultArray = [UserClass]()
for user in users.children {
let user = UserClass(snapshot: user as! DataSnapshot)
if user.uid == self.job.userID {
let appRef = self.ref.child("jobs").child(self.job.postID).child("applicants")
appRef.queryOrderedByKey().observeSingleEvent(of: .childAdded, with: { (snapshot) in
let sValue = snapshot.value
resultArray.append(user)
})
}
}
}) { (error) in
print(error.localizedDescription)
}
}
This is what my database looks like where the User's UIDs are stored.
jobs
"Job ID"
applicants:
-KtLJaQnFMnyI-MDWpys:"8R6ZAojX0FNO7aSd2mm5aQXQFpk1"
-KtLLBFU_aVS_xfSpw1k:"GGqjtYvwSwQw9hQCVpF4lHN0kMI3"
If I was to run the app, it fetches UID: "8R6ZAojX0FNO7aSd2mm5aQXQFpk1"
How can I implement a for loop or an if statement to ensure that all of the values are taken and appended into the table view
I know that I need a for loop before the fetchApplicants is called from AuthService because it is only fetching one UID but I can't work out where it would go.
Thanks.
P.S. This is what I have tried
func loadApplicants() {
let jobID = job.postID
let appRef = ref.child("jobs").child(jobID!).child("applicants")
appRef.queryOrderedByKey().observeSingleEvent(of: .childAdded, with: { (snapshot) in
if let applicants = snapshot.value! as? [String:AnyObject] {
for (value) in applicants {
self.authService.fetchApplicants(applicantID: "\(value!)", completion: { (users) in
self.usersArray = users
self.tableView.reloadData()
})
}
}
})
}
but the output is:
(key: "-KtLLBFU_aVS_xfSpw1k", value: GGqjtYvwSwQw9hQCVpF4lHN0kMI3)
(key: "-KtLJaQnFMnyI-MDWpys", value: 8R6ZAojX0FNO7aSd2mm5aQXQFpk1)
Needed to use observe instead of observeSingleEvent
Answer:
appRef.queryOrderedByKey().observe(.childAdded, with: { (snapshot) in
I have this function that is supposed to fetch data from a comments node from firebase. I want to implement pagination to not load 100+ comments at once. Everything seems to be working but my code seems to be failing at casting the snapchat.value to a Dictionary
func fetchComments(){
messagesRef = Database.database().reference().child("Comments").child(eventKey)
var query = messagesRef?.queryOrderedByKey()
if comments.count > 0 {
let value = comments.last?.commentID
query = query?.queryStarting(atValue: value)
}
query?.queryLimited(toFirst: 2).observe(.childAdded, with: { (snapshot) in
var allObjects = snapshot.children.allObjects as? [DataSnapshot]
allObjects?.forEach({ (snapshot) in
// print out snapshot and it isn't empty
print(snapshot.value) // here it keeps going into the else statement even though snapshot.value clearly exist.
guard let commentDictionary = snapshot.value as? [String:Any] else{
return
}
print(commentDictionary)
})
}) { (err) in
print("Failed to observe comments")
}
}
My question is can anyone take a look at this and maybe see where I went wrong? My code looks fine to me and I can't see what's is wrong.
My tree looks like this
"Comments" : {
"CCDS" : {
"-KrrsXkj6FznzRD0-Xzs" : {
"content" : "Shawn",
"profileImageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/profile_images%2FBC868F8F-E9EC-4B9D-A248-DD2187BC140C.PNG?alt=media&token=fb14700c-2b05-4077-b45c-afd3de705801",
"timestamp" : 1.503102381340935E9,
"uid" : "oxgjbrhingbf7vbaHpflhw6G7tB2"
}
},
"MIA" : {
"-Krghz9d5_CPjkmdffef" : {
"content" : "22",
"profileImageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/profile_images%2FF50F6915-DEAB-4A5B-B1AB-CABC1E349148.PNG?alt=media&token=4eb7c708-ec87-45bf-952d-0bd410faee50",
"timestamp" : 1.502915064803007E9,
"uid" : "oxgjbrhingbf7vbaHpflhw6G7tB2"
},
"-KrpoEnNYsmRZ5guORUj" : {
"content" : "23",
"profileImageURL" : "https://firebasestorage.googleapis.com/v0/b/eventful-3d558.appspot.com/o/profile_images%2FBC868F8F-E9EC-4B9D-A248-DD2187BC140C.PNG?alt=media&token=fb14700c-2b05-4077-b45c-afd3de705801",
"timestamp" : 1.503067700479352E9,
"uid" : "oxgjbrhingbf7vbaHpflhw6G7tB2"
}
}
}
Based off my code it bypasses the key and goes straight to the children.
For example if pass in MIA it should go to MIA and grab the key corresponding to each comment "-KrrsXkj6FznzRD0-Xzs" and "-KrpoEnNYsmRZ5guORUj" but it is returning everything under that unique ID instead. Which is a problem
The code in your callback seems to assume that you get called with a collection of comments. To get such a collection you need to observe the .value event. When you observe the .value event, you callback gets invoked with a single snapshot that contains all the nodes matching the query:
query?.queryLimited(toFirst: 2).observe(.value, with: { (snapshot) in
var allObjects = snapshot.children.allObjects as? [DataSnapshot]
allObjects?.forEach({ (snapshot) in
print(snapshot.key)
print(snapshot.value)
guard let commentDictionary = snapshot.value as? [String:Any] else{
return
}
print(commentDictionary)
})
}) { (err) in
print("Failed to observe comments")
}
When you observe .childAdded, your callback instead gets called for every individual node matching the query. That means you need to get rid of a loop in your code:
query?.queryLimited(toFirst: 2).observe(.childAdded, with: { (snapshot) in
print(snapshot.key)
print(snapshot.value)
guard let commentDictionary = snapshot.value as? [String:Any] else{
return
}
print(commentDictionary)
}) { (err) in
print("Failed to observe comments")
}
I'm using the following query to get the snapshot below.
dbRef.child("users").queryOrdered(byChild: "username").queryStarting(atValue: text).queryEnding(atValue: text+"\u{f8ff}").observe(.value, with: { snapshot in })
But I'm having trouble figuring out how to iterate over the values of the children "username" (i.e. bill, billy, billykins) because they all have the same key ("username"). I'm trying to extract all the names and put them in an array of names.
Snap (users) {
fDrzmwRUt2guh3O8pc792ipyEqA3 = {
username = bill;
};
qyQkIOxSpXgQoUoh0QNvPlkQ1Mp1 = {
username = billy;
};
edSk54xSpXgQoYoh0QNvOlkQ1Mp3 = {
username = billykins;
};
}
This is my function which gets the snapshot and tries to iterate over it. However, the loop crashes:
func findUsers(text: String) {
print("search triggered")
dbRef.child("users").queryOrdered(byChild: "username").queryStarting(atValue: text).queryEnding(atValue: text+"\u{f8ff}").observe(.value, with: { snapshot in
print(snapshot)
for i in snapshot.children{
let value = snapshot.value as! Dictionary<String,String>
let username = value["username"]
print(username)
self.userList.append(username!)
print(self.userList)
}
}) { (error) in
print("searchUsers \(error.localizedDescription)")
}
}
Here's a fraction of the log. Too long to post:
0x1002cg360 <+272>: adr x9, #268929 ; "value type is not bridged to Objective-C"
0x1002cg364 <+276>: nop
0x1002cg368 <+280>: str x9, [x8, #8]
-> 0x1002cg36c <+284>: brk #0x1
0x1002cg370 <+288>: .long 0xffffffe8 ; unknown opcode
Here's the solution I was looking for. I needed to loop through the big snapshot to extract the child snapshots into an array, and then loop through the child snapshots by value to get the usernames:
func findUsers(text: String) {
print("search triggered")
dbRef.child("users").queryOrdered(byChild: "username").queryStarting(atValue: text).queryEnding(atValue: text+"\u{f8ff}").observe(.value, with: { snapshot in
print(snapshot)
if ( snapshot.value is NSNull ) {
print("not found")
} else {
var blaArray = [FIRDataSnapshot]()
for child in snapshot.children {
let snap = child as! FIRDataSnapshot //downcast
blaArray.append(snap)
}
for child in blaArray {
let dict = child.value as! NSDictionary
let username = dict["username"]!
print(username)
}
}) { (error) in
print("searchUsers \(error.localizedDescription)")
}
}
Adapted from this post: Get data out of array of Firebase snapshots