I have been trying to fetch data from Firebase using Realtime database. I want to check the contacts in iPhone and then if any contact number matches with that of any number in "numbers" table in db, then I have to get the user_key from it and then using that key, I have to obtain the corresponding details from users table.
for number in numbers {
Database.database().reference().child("numbers/\(number)").observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
let userKey = snapshot.value as! String
// We found this user, no determine there name, (TODO has_image?)
Database.database().reference().child("users/\(userKey)/public/name").observeSingleEvent(of: .value, with: { (namesnapshot) in
if namesnapshot.exists() {
let name = namesnapshot.value as! String
print("FOUND \(name)")
complete(.success((userID: userKey, name: name)))
}
})
} else {
if numbers.index(of: number) == numbers.count - 1 { // Last Number checked and not found yet, so fail
complete(.failure(UserApiError.UserNotFound))
}
}
})
}
numbers is the array of contact numbers for a particular contact. For a contact having single number, this works fine. But for contacts having multiple numbers, the
Database.database().reference().child("users/\(userKey)/public/name").observeSingleEvent(of: .value, with: { (namesnapshot) in
will call after some time due to which the next index in the for loop gets called. So even if I have the data in first number in a contact, it will return failure because the next number will be iterated before the success of the observeSingleEvent.
I have been sitting for hours now, no ideas left with me. Please help!
I think a better approach is:
1 - Get all numbers from DB.
2 - Get all contact numbers that exists on DB.
3 - Finally, get the name of that contacts.(Exactly the way you are doing).
OBS: To do that you must change your DB. Your numbers must be saved as key-value pair. For exemple "555-0000" : true.
Database.database().reference().child("numbers").observeSingleEvent(of: .value, with: { (snapshot) in
guard let numbersFromDB = snapshot.value as? [String: Any] else{
print("Fail get numbers from db")
}
let numbersMatchedOnDB = numbersFromDB.keys.filter{ numbers.contains($0) }//get numbers from contact that exist on DB.
if numbersMatchedOnDB.isEmpty{
complete(.failure(UserApiError.UserNotFound))
}
else{
//For each contact number that exist on DB. it gets its name.
numbersMatchedOnDB.forEach{ numberMatchedOnDB in
Database.database().reference().child("numbers/\(numberMatchedOnDB)").observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() {
let userKey = snapshot.value as! String
// .... nothing changed here ....
}
})
}
}
})
Related
When I want to observe I run:
let likesRef = Database.database().reference().child("likes").child(postId)
likesRef.observeSingleEvent(of: .value, with:{ (snapshot) in
let likes = snapshot.childrenCount
let totalLikes = Int(likes)
// display totalLikes
})
When I want to post I run:
let dict = [uid: 1]
let likesRef = Database.database().reference().child("likes").child(postId)
likesRef.updateChildValues(dict) { [weak self](error, ref) in
if let error = error { return }
// if no error then update the ref
})
When posting the completionBlock has 2 values:
withCompletionBlock: (Error?, DatabaseReference)
Is there a way that I can also observe the ref that I am posting to using the 2nd completionBlock value: DatabaseReference:
For eg once the user likes something I want to update the ref and display the new number of likes at the same time without having to run observeSingleEvent:
let dict = [uid: 1]
let likesRef = Database.database().reference().child("likes").child(postId)
likesRef.updateChildValues(dict) { (error, ref) in
if let error = error { return }
// *** somehow get the total amount of likes from the ref ***
// If possible I want to avoid this code below
likesRef.observeSingleEvent(of: .value, with:{ (snapshot) in
let likes = snapshot.childrenCount
let totalLikes = Int(likes)
// display totalLikes
})
})
Actually its not possible to get both Event at same time. Once you like once your data reach at firebase database then you will get Value,Change,ChieldAdded event on App side. It will take 1-2 second or less depend on Internet. So Post will call first and then observer will call.
You can get observer this by two ways:
Step 1 : Add Child Change listener
let likesRef = Database.database().reference().child("likes").child(postId)
likesRef.observe(.childChanged, with: {
(snapshot) in
let likes = snapshot.childrenCount
let totalLikes = Double(Int(likes))
// display likes
})
Child change listener listens changes on snapshot
Step 2 : Put value listener
let likesRef = Database.database().reference().child("likes").child(postId)
likesRef.observe(.value, with: {
(snapshot) in
let likes = snapshot.childrenCount
let totalLikes = Double(Int(likes))
// display likes
})
Value listener listens every time
I Hope this will help...
Here's some very abbreviated code to accomplish the task of adding a users uid who likes a post and incrementing a counter via runTransactionBlock. Keep in mind there are 100 ways to do this.
A proposed structure
all_posts
post_0
like_count: 2
post: "Hello, World"
likes
post_0
uid_0: true
uid_1: true
Based on the question and discussion, I broke the posts and likes into separate nodes. The reasoning is that when the posts are loaded, they will probably be displayed in a list and all that's really needed at that point is the post topic and the total number of likes, so I made 'like_count' part of the post node.
If we added the actual likes within the post node itself, it could be 10,000 or 10,000,000 and there's no reason to load all of that data when loading in the posts. Having that many likes could also overwhelm the device.
Within the likes node, each post key references the post in the all_posts node. The children are the uid's of the users that liked the post and the value is a boolean 'true' as a placeholder. Nodes with no values cannot exist so 'true' keeps it in place and is a tiny amount of data.
Then the code -
func updatePostWithLikesViaTransaction() {
let postsRef = self.ref.child("all_posts") //self.ref points to my Firebase
let thisPostRef = postsRef.child("post_0")
thisPostRef.runTransactionBlock ({ (currentData: MutableData) -> TransactionResult in
if var data = currentData.value as? [String: Any] {
var count = data["like_count"] as? Int ?? 0
count += 1
data["like_count"] = count
currentData.value = data
}
return TransactionResult.success(withValue: currentData)
}) { (error, committed, snapshot) in
if let error = error {
print(error.localizedDescription)
return
}
print("successfully incremented counter")
let likesRef = self.ref.child("likes")
let likesPostRef = likesRef.child(thisPostRef.key!)
likesPostRef.child("uid_2").setValue(true)
}
}
The above is not ideal by any means but demonstrates the process (and works with the presented structure).
First we get a reference to the post we want to update and then within a transaction block read the currentData 'like_count' child which would return 2 based on the values in the structure. That's incremented to 3, updated within currentData and then updated via the TransactionResult.
runTransactionBlock also has an optional completion callback and we are using that to, upon success, update the post within the likes with the users uid and true.
The end result of running this is that the counter is incremeted to 3 and 'uid_2: true' is added to the 'likes/post_0' node
I am facing a serious callback hell on firebase realtime database update.
Situation:
I have comments node which store all the comment's detail information, such as belong to whose userId (uid) , message, and post id (pid). Please see image below.
I have another post-comment nodes, which store comments key under each post id key. Please see image below.
Finally the third nodes is user-comment, which store all comments key under unique user account id key. Please see image below.
Problem:
Everything work fine on "Write comment" function, because it just create a comment key and update comment data to these nodes.
But, when user call "Delete post" function, which will delete all the comments data belong to this post id. Therefore, I have this code logical to loop all the comments data. The whole point is that first I have to get the post-comment snapshot in order to limitation the query amount on comments node (because comments node store all the app user's comment detail data. Without knowing the quantity of comment belong to the target post, it will need to for loop all over the comments node, it is too overload.)
For looping the post-comment will get the commentKey, then I can set Null on comments node and post-comment node.
But the issues happen on I need to use comments node to find out the userId, in order to set NSNull on user-comment. When I calling the event below:
commentsRef.child((snap as AnyObject).key).observeSingleEvent(of:
.value, with: { (commentSnapshot) in
})
The commentsRef callback scope become another thread. Therefore, if I call rootRef.updateChildValues out side of this scope and in the end of for loop (post-comment) which will only update comments node and post-comment node. The user-comment updates data will still assign key:value on the other thread.
updates["user-comment/(userId)/comments/(commentKey)"] = NSNull()
I have to put the rootRef.updateChildValue in the
commentsRef.child((snap as AnyObject).key).observeSingleEvent(of:
.value, with: { (commentSnapshot) in
...
rootRef.updateChildValues(updates)
})
This logic will cause updateChildValues being called too many time if the comments over 10,000 or more than 1 million, because it is in the for looping. I use count down method try to call update only once on the for loop end. But the count number always be 0 in the commentRef scope... I don't know why...
Please help me out with a better solution to dealing with this nested observeSingleEvent update issues without changing the current nodes structure. My goal is to only call rootRef.updateChildValue one time.
Thanks for your help.
Demo code:
func deleteAllCommentsRelateTo(postId: String, callback: ((CommentServiceError?) -> Void)?) {
var error: CommentServiceError?
guard session.isValid else {
error = .authenticationNotFound(message: "Authentication not found.")
callback?(error)
return
}
let uid = session.user.id
let rootRef = Database.database().reference()
let path1 = "posts/\(postId)/comments_count"
let path2 = "posts/\(postId)/uid"
let commentCountRef = rootRef.child(path1)
let authorRef = rootRef.child(path2)
authorRef.observeSingleEvent(of: .value, with: { authorSnapshot in
guard let authorId = authorSnapshot.value as? String else {
error = .failedToDelete(message: "Author not found")
callback?(error)
return
}
if uid != authorId {
error = .failedToDelete(message: "User has no permission to delete this post comments")
callback?(error)
return
}
commentCountRef.runTransactionBlock({ (data) -> TransactionResult in
if let _ = data.value as? Int {
data.value = 0
}
return TransactionResult.success(withValue: data)
}) { (err, committed, snapshot) in
guard err == nil, committed else {
error = .failedToDelete(message: "Unable to delete a comment")
callback?(error)
return
}
var updates: [AnyHashable: Any] = [:]
/**
* [CHECKED] Set NSNull() on comments, post-comment, and user-comment nodes.
*/
let commentsRef = rootRef.child("comments")
let postCommentRef = rootRef.child("post-comment")
let query = postCommentRef.child(postId).child("comments").queryOrderedByKey()
query.observeSingleEvent(of: .value, with: { (data) in
guard data.hasChildren() else {
error = .failedToDelete(message: "No comments data")
callback?(error)
return
}
var count = data.childrenCount
print("post-comment count!!!!!!!: ", data.childrenCount)
for snap in data.children {
guard let commentKeySnap = snap as? DataSnapshot else {
continue
}
count -= 1
let commentKey = commentKeySnap.key
if count == 0 {
print("this is totally not right!!!!!")
}
updates["comments/\(commentKey)"] = NSNull()
updates["post-comment/\(postId)/comments/\(commentKey)"] = NSNull()
commentsRef.child((snap as AnyObject).key).observeSingleEvent(of: .value, with: { (commentSnapshot) in
guard let userId = commentSnapshot.childSnapshot(forPath: "uid").value as? String else {
return
}
updates["user-comment/\(userId)/comments/\(commentKey)"] = NSNull()
print("In this observeSingleEvent will always be 0 count::::: ", count)
if count == 0 {
rootRef.updateChildValues(updates, withCompletionBlock: { err, ref in
guard err == nil else {
error = .failedToDelete(message: "Failed to delete comment")
callback?(error)
return
}
})
print("deleteAllComments: ", updates)
callback?(nil)
}
})
print("count down: ", count)
}
})
})
}
})
}
Solution:
I accidentally found out the correct place to put count -= 1. Originally I put it in the for loop scope, but the count did not decrease in the commentRef in scope. Therefore, I put count -= 1 in the commentRef scope which success count to zero and only call rootRef.update one time.
My data structure is as follows:
users:
user1:
-carModel: evo x
-username: importguy
-region: north east
user2:
-carModel: evo x
-username: evoguy
-region: north east
user3:
-carModel: mustang gt
-username: muscleguy
-region: south east
I want the user to be able to search for a car, say evo, and display results of users who own those particular cars. I need to paginate these results for my app. The problem is I can't figure out how to properly query this. Here is what i have so far.
func fetchUsersBy(car: String) {
if self.carCurrentKey == nil {
let ref = USER_REF.queryOrdered(byChild: "carModel").queryStarting(atValue: car).queryLimited(toFirst: 3)
ref.observeSingleEvent(of: .value, with: { (snapshot) in
guard let snap = snapshot.children.allObjects as? [FIRDataSnapshot] else { return }
guard let last = snapshot.children.allObjects.last as? FIRDataSnapshot else { return }
snap.forEach({ (snapshot) in
guard let userDict = snapshot.value as? Dictionary<String, AnyObject> else { return }
guard let carModel = userDict["carModel"] as? String else { return }
if carModel.contains(car) {
print(snapshot)
}
})
self.carCurrentKey = last.key
self.carCurrentValue = last.childSnapshot(forPath: "carModel").value as? String
})
} else {
// where to start next query?
let ref = USER_REF.queryOrder(byChild: "carModel").queryStarting(atValue: self.carCurrentValue)
}
}
I have to order the query by carModel, in order to group all of the users with that particular car type together in a snapshot. Since all the car models are the same value, I cannot figure out where to start or end the next query for the pagination. Using the reference i have in the else block starts the query at the same place as the block above. Any help or advice would be much appreciated.
I considered doing a fan out, and making a separate structure for car types. This would be difficult though.
For both startAt() and endAt(), you can pass a second value, childKey as shown here.
So your query will look something like this:
let ref = USER_REF.queryOrdered(byChild: "carModel").queryStarting(atValue: self.carCurrentValue, childKey: self.carCurrentKey).queryLimited(toFirst: 3+1)
Note that I used toFirst: 3+1. That's because, annoyingly, startAt() is inclusive and there's no way to skip the first record. So, since we started from the last record retrieved on the previous page, you will want to query for one extra record and discard the first result.
Here's a more complete example in JavaScript. Not familiar enough to translate this to Swift, but it should give you the algorithm in completion.
class Cursor {
constructor(baseRef, pageSize) {
this.baseRef = baseRef;
this.lastKey = null;
this.lastValue = null;
this.pageSize = pageSize;
}
next() {
let ref = this.baseRef;
if( this.lastValue !== null ) {
// a previous page has been loaded so get the next one using the previous value/key
// we have to start from the current cursor so add one to page size
ref = ref.startAt(this.lastValue, this.lastKey).limitToFirst(this.pageSize+1);
}
else {
// this is the first page
ref = ref.limitToFirst(this.pageSize);
}
return ref.once('value').then(snap => {
const keys = [];
const data = []; // store data in array so it's ordered
snap.forEach(ss => {
data.push(ss.val());
keys.push(ss.key);
});
if( this.lastValue !== null ) {
// skip the first value, which is actually the cursor
keys.shift();
data.shift();
}
// store the last loaded record
if( data.length ) {
const last = data.length - 1;
this.lastKey = keys[last];
this.lastValue = data[last].author;
}
return data;
});
}
}
And here's a working fiddle.
Keep in mind that this is a realtime data stream. So pagination is tricky. It's generally easier to just do infinite scroll than to try and maintain a realistic cursor on a moving data set (records can reorder when data changes, get deleted, added in the middle, etc).
I have a Firebase structure that looks like:
- key1
-key2
-key3:value
-key4:value
-key5:value
-key6:value
I am looking to return records where key3's value equals a particular string.
let ref = FIRDatabase.database().reference()
let path = "Object/key1/key2"
ref.child(path).queryOrdered(byChild: "key3").queryEqual(toValue: "myvalue").observeSingleEvent(of: .value, with: {(snapshot) in
The above returns NULL. If I remove the queryEqual, all records are returned. I have triple checked that the "myvalue" is matching in FB as well as in the call.
I have the FB call in a loop as key1 and key2 change. In the end I only want those records (everything under key2) returned only if key3 is equal to value I send in my queryEqual statement.
To give the full return see below. I commented out my actual return process to just check via a simple print:
ref.child(path).queryOrdered(byChild: "key3").queryEqual(toValue: "mvValue").observeSingleEvent(of: .value, with: {(snapshot) in
for test in snapshot.children
{
print (test)
}
/*if let returnDict = snapshot.value as? NSDictionary
{
helperProtocol.firebaseDidReturn?(returnDict: returnDict, extraDict: extraDict, name:name)
}
else if let returnArray = snapshot.value as? NSArray
{
helperProtocol.firebaseDidReturn?(returnDict: ["array":returnArray], extraDict: extraDict, name:name)
}
else
{
helperProtocol.firebaseDidReturn?(returnDict: nil, extraDict: extraDict, name:name)
}*/
})
The issue was the depth of the query path. From the above I was using:
let path = "Object/key1/key2"
The path needed to be:
let path = "Object/key1"
So even though the search key (key3) is under key2, the approach is to go one level higher as shown above.
I've got a class that has Title, users and a timestamp.
My database is set up like :
users
ablksjdlf39493
rooms
room1: true
rooms
room1
timestampOfLastPost: 39403942
users
039403fsjlkj: true
;alkjsdksdkj: true
I'm running a query on my user's rooms and grabbing the snapshot.key to get in this example "room1". Then inside of the first query I run another query and I use that key as a child reference to my rooms node to go to that room (rooms-->room1), and set is as my class object's title. From the 2nd query I'm pulling out the timestamp and use that for my object's timestamp.
I'm a bit confused how to get the childcount of out users.
I was running yet another nested query inside of my second query. But then I was getting all sorts of weird duplicate posts being added to my tableview when I was loading them. And that just doesn't seem very efficient anyways.
Is there a way in my second query to get both the timestamp and the children.count of my users node? The only way I've seen to do that is to run an observer on the specific node and do a snapshot.childrenCount.
edit:
currentUserFirebaseReference.child("rooms").observeEventType(.Value) { (snapshot: FIRDataSnapshot) in
self.interestsArray = []
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots {
let eachInterest = Interest()
let interestKey = snap.key
let title = snap.key.uppercaseString
eachInterest.title = title
//grabbing the user's current rooms and getting the snap.key to use for my next query.
DataService.ds.REF_INTERESTS.child(interestKey).observeEventType(.Value, withBlock: { (snapshot: FIRDataSnapshot) in
if let lastuser = snapshot.value!["lastJoin"] as? Int {
eachInterest.latestUser = lastuser
} else {
print("couln't pull that value")
}
//getting the timestamp
DataService.ds.REF_INTERESTS.child(interestKey).child("users").observeEventType(.Value, withBlock: { (snapshot: FIRDataSnapshot) in
// I can get the users children.count by doing yet another query, but my
// interestsArray gets all messed up and I get duplicates / weird
// loading in my tableview. So I'm looking to not do this whole
// separate query and just grab it from up above where I get the
// timestamp?
let snapshotChildren = String(Int(snapshot.childrenCount))
eachInterest.users = snapshotChildren
self.interestsArray.append(eachInterest)
//self.interestsArray.sortInPlace({ $0.latestUser < $1.latestUser })
dispatch_async(dispatch_get_main_queue(), {
self.tableView.reloadData()
})
})
})
}
}
}
}