How to use Firestore query pagination with TableVIew - ios

I am trying to use Firestore pagination with swift TableView. Here is my code which loads the first 4 posts from firestore.
func loadMessages(){
let postDocs = db
.collectionGroup("userPosts")
.order(by: "postTime", descending: false)
.limit(to: 4)
postDocs.addSnapshotListener { [weak self](querySnapshot, error) in
self?.q.async{
self!.posts = []
guard let snapshot = querySnapshot else {
if let error = error {
print(error)
}
return
}
guard let lastSnapshot = snapshot.documents.last else {
// The collection is empty.
return
}
let nextDocs = Firestore.firestore()
.collectionGroup("userPosts")
.order(by: "postTime", descending: false)
.start(afterDocument: lastSnapshot)
if let postsTemp = self?.createPost(snapshot){
DispatchQueue.main.async {
self!.posts = postsTemp
self!.tableView.reloadData()
}
}
}
}
}
func createPost(_ snapshot: QuerySnapshot) ->[Post]{
var postsTemp = [Post]()
for doc in snapshot.documents{
if let firstImage = doc.get(K.FStore.firstImageField) as? String,
let firstTitle = doc.get(K.FStore.firstTitleField) as? String,
let secondImage = doc.get(K.FStore.secondImageField) as? String,
let secondTitle = doc.get(K.FStore.secondTitleField) as? String,
let userName = doc.get(K.FStore.poster) as? String,
let uID = doc.get(K.FStore.userID) as? String,
let postDate = doc.get("postTime") as? String,
let votesForLeft = doc.get("votesForLeft") as? Int,
let votesForRight = doc.get("votesForRight") as? Int,
let endDate = doc.get("endDate") as? Int{
let post = Post(firstImageUrl: firstImage,
secondImageUrl: secondImage,
firstTitle: firstTitle,
secondTitle: secondTitle,
poster: userName,
uid: uID,
postDate: postDate,
votesForLeft: votesForLeft,
votesForRight:votesForRight,
endDate: endDate)
postsTemp.insert(post, at: 0)
}else{
}
}
return postsTemp
}
Here is my delegate which also detects the end of the TableView:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let post = posts[indexPath.row]
let cell = tableView.dequeueReusableCell(withIdentifier: K.cellIdentifier, for: indexPath) as! PostCell
cell.delegate = self
let seconds = post.endDate
let date = NSDate(timeIntervalSince1970: Double(seconds))
let formatter = DateFormatter()
formatter.dateFormat = "M/d h:mm"
if(seconds <= Int(Date().timeIntervalSince1970)){
cell.timerLabel?.text = "Voting Done!"
}else{
cell.timerLabel?.text = formatter.string(from: date as Date)
}
let firstReference = storageRef.child(post.firstImageUrl)
let secondReference = storageRef.child(post.secondImageUrl)
cell.firstTitle.setTitle(post.firstTitle, for: .normal)
cell.secondTitle.setTitle(post.secondTitle, for: .normal)
cell.firstImageView.sd_setImage(with: firstReference)
cell.secondImageView.sd_setImage(with: secondReference)
cell.userName.setTitle(post.poster, for: .normal)
cell.firstImageView.layer.cornerRadius = 8.0
cell.secondImageView.layer.cornerRadius = 8.0
if(indexPath.row + 1 == posts.count){
print("Reached the end")
}
return cell
}
Previously I had an addSnapshotListener without a limit on the Query and just pulled down all posts as they came. However I would like to limit how many posts are being pulled down at a time. I do not know where I should be loading the data into my model. Previously it was being loaded at the end of the addSnapshotListener and I could still do that, but when do I use the next Query? Thank you for any help and please let me know if I can expand on my question any more.

There is a UITableViewDelegate method called tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) that will be called just before a cell is loading.
You could use this one to check if the row at IndexPath is in fact the cell of the last object in your tableview's datasource. Something like datasource.count - 1 == IndexPath.row (The -1 is to account for item 0 being the first item in an array, where as it already counts as 1).
If that object is indeed the last one in your datasource, you could make a call to Firebase and add items to the datasource. Before mutating the datasource, make sure to check the new number of objects the show (the ones already loaded + new ones) has to be larger than the current number of objects in the datasource, otherwise the app will crash.
You also might want to give your user a heads up that you're fetching data. You can trigger that heads up also in the delegate method.

Related

Repeating the same query snapshot, bringing in same data, despite new data being added to firestore

I have been following the documentation to create a query search in my database to obtain the top scores to display in a tableView.
The code below works, however, when a new (higher score) is added, the tableview is still displaying the old query data.
E.g I have three top scores in my database.. [121, 131, 134]. After the first query these are displayed correctly.
I then continue to play and add some more scores, [121, 131, 134, 234, 432] but the same results are shown in my tableView [121, 131, 134].
I am limiting my display to three items. So it should really show ..... [134, 234, 432].
I have tried clearing my tableView with
scoresArray.removeAll()
topScoresTableView.reloadData()
(This is called when I leave the VC) But this had no effect.
class ScoreClass {
let db = Firestore.firestore()
var name = ""
var score = 0
init(withName: String, andScore: Int) {
name = withName
score = andScore
}
}
let ref = Database.database().reference()
func retrieveUserData() {
let postsRef = self.db.collection("users")
let query = postsRef
.whereField("highScore", isGreaterThan: 5000)
.order(by: "highScore", descending: false)
.limit(to: 3)
query.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
print("\(document.documentID) => \(document.data())")
let dict = document.data()
let name = dict["username"] as! String
let score = dict["highScore"] as! Int
let aScore = ScoreClass(withName: name, andScore: score)
self.scoresArray.insert(aScore, at: 0)
}
self.topScoresTableView.reloadData()
}
}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.scoresArray.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = topScoresTableView.dequeueReusableCell(withIdentifier: textCellIdentifier, for: indexPath) as! TableViewCell
let row = indexPath.row
let scoreClassObject = scoresArray[row]
let name = scoreClassObject.name
let score = scoreClassObject.score
cell.backgroundColor = UIColor.clear
cell.usernameLabel.text = name
cell.resultLabel.text = String(score)
cell.rankNumberLabel.text = "\(indexPath.row + 1)"
print(scoresArray)
return cell
}
Your code isn't arranging to receive realtime updates from Firestore. It is just querying Firestore a single time with getDocuments().
What you will have to do instead is change your code to listen to realtime updates using addSnapshotListener(), then update your TableView every time your listener is invoked, when the results of the query change over time.

Multiple Table View with different arrays

I have a detail view that shows the details of an event, the people who participate and the people who asked to participate. I have created two arrays of different types but they have the same fields, only that a first structure represents the users with the 'status_confirm' field equal to 1 (therefore Accepted Users), while the other has as 'status_confirm' equal to 0 (Users awaiting acceptance). I declared two arrays, the first one: var arrayUserAccepted = [User_accepted] ().
The second one: var arrayUserWaiting = [User_waiting] (). Struct Image
Next step: I populate these structures via a php script
func getData(){
let url = URL(string: “MYURL”)
URLSession.shared.dataTask(with:url!, completionHandler: {(data, response, error) in
guard let data = data, error == nil else { return }
do {
let json = try JSONSerialization.jsonObject(with: data, options: []) as! [String:AnyObject]
print("JSON: \n\(json)\n")
let waiting = json["waiting"] as! [AnyObject]
let accepted = json["accepted"] as! [AnyObject]
DispatchQueue.main.async {
for list_user_waiting in waiting {
let id_user_waiting = list_user_waiting["id_user”] as! String
let name_user_waiting = list_user_waiting[“name_user”] as! String
let email_user_waiting = list_user_waiting["email"] as! String
var photo_user_waiting = list_user_waiting[“photo”]
let status_user_waiting = list_user_waiting["status”] as! String
if photo_user_waiting is NSNull {
photo_user_waiting = ""
}
let listUserWaiting = User_waiting(id_user_waiting: id_user_waiting, name_user_waiting: name_user_waiting, email_user_waiting: email_utente_attesa, foto_waiting: photo_user_waiting as! String, status_waiting: status_user_waiting)
self.arrayUserWaiting.append(listUserWaiting)
self.tableViewListUserWaiting.reloadData()
}
for list_user_accepted in accepted {
let id_user_accepted = list_user_accepted["id_utente"] as! String
let name_user_accepted = list_user_accepted["name_utente"] as! String
let email_user_accepted = list_user_accepted["email"] as! String
var photo_user_accepted = list_user_accepted[“photo"]
let status_user_accepted = list_user_accepted["status”] as! String
if photo_user_accepted is NSNull {
photo_user_accepted = ""
}
let listUserAccepted = User_accepted(id_user: id_user_accepted, nome_utente: name_user_accepted, email: email_user_accepted, foto: photo_user_accepted as! String, stato: status_user_accepted)
self.arrayUserAccepted.append(listUserAccepted)
self.tableViewListUserAccepted.reloadData()
}
}
} catch let error as NSError {
print(error)
}
}).resume()}
This above is a function that I call in the viewDidLoad(). The next step would be to use the functions of the table view and it is here that I think there is the injunction
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
var count: Int?
if tableView == self.tableViewListUserAccepted {
count = arrayUserAccepted.count
}
if tableView == self.tableViewListUserWaiting {
count = arrayUserWaiting.count
}
return count!
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
if tableView == self.tableViewListUserAccepted {
cell.imageProfileUserAccepted.image = UIImage(named: "imageDefault")
cell.valueSliderUserAccepted.value = Float(50) //JUST FOR POPULATE THE INTERFACE
cell.name_user_accepted.text = arrayUserAccepted[indexPath.row].name_user
}
if tableView == self.tableViewListUserWaiting {
cell.imageProfileUserWaiting.image = UIImage(named: "imageDefault")
cell.valueSliderUserWaiting.value = Float(23) //JUST FOR POPULATE THE INTERFACE
cell.name_user_waiting.text = arrayUserWaiting[indexPath.row].name_user_waiting
}
return cell
}
Once done all this round, I start the application but nothing. The tables are empty. In the console the script answers me correctly and so I can not figure out where the error could be. Needless to say, I have declared the .delegate and .dataSource of both tables, both in the Main.Storyboard and in the code.
Everything is fine just change the format of IF condition and it will work.
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
var count: Int?
if tableView == self.tableViewListUserAccepted {
count = arrayUserAccepted.count
} else {
count = arrayUserWaiting.count
}
return count!
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if tableView == self.tableViewListUserAccepted {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
cell.imageProfileUserAccepted.image = UIImage(named: "imageDefault")
cell.valueSliderUserAccepted.value = Float(50) //JUST FOR POPULATE THE INTERFACE
cell.name_user_accepted.text = arrayUserAccepted[indexPath.row].name_user
return cell
} else {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
cell.imageProfileUserWaiting.image = UIImage(named: "imageDefault")
cell.valueSliderUserWaiting.value = Float(23) //JUST FOR POPULATE THE INTERFACE
cell.name_user_waiting.text = arrayUserWaiting[indexPath.row].name_user_waiting
return cell
}
}
Also check if the datasource and delegate of both of your tableView are set. Finally call the tableView.reloadTable() method on both of your tableviews after you populate your arrays in the viewDidLoad() method.

UITableView with core data pushing incorrect index and data

I've been struggling with this for several days already. There are similar problems in this website, but not very the same. And I didn't manage to go forward. I will try to simplify it with one variable.
Problem:
After filtering records in UITableView (records are taken from core data) and trying to push data to another viewcontroller, I get unfiltered index for data, so incorrect data is pushed to new view controller.
My code is below:
I set global variable for core data:
var events : [Event] = []
#objc func textFieldDidChange(_ textField: UITextField) {
if searchField.text == "" {
filterAdded = false
} else {
filterAdded = true
let request:NSFetchRequest<Event> = Event.fetchRequest()
let predicate = NSPredicate(format: "name CONTAINS[c] %# AND nearestDate >= %#", searchField.text!, currentCorrectDate! as CVarArg)
request.predicate = predicate
let sortDescriptor = NSSortDescriptor(key: "nearestDate", ascending: true)
request.sortDescriptors = [sortDescriptor]
do {
events = try DatabaseController.getContext().fetch(request)
}
catch {
print("Error: \(error)")
}
mainListOfDates.reloadData()
}
}
}
It is triggered every time some character is added to search field. UITableView name is "mainListOfDates".
This function works properly and calculated only filtered events:
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return events.count }
This function shows all records from core data in UITableView cells:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "eventCell", for: indexPath) as! EventTableViewCell
let event = events[indexPath.row]
cell.eventNameLabel.text = event.value(forKeyPath: "name") as? String
return cell
}
And with "didSelectRowAt" I would like to push filtered or unfiltered (works perfectly with unfiltered) data to new view controller:
let Storyboard = UIStoryboard(name: "Main", bundle: nil)
let eventStoryboard = Storyboard.instantiateViewController(withIdentifier: "EventViewController") as! EventViewController
let cell = tableView.dequeueReusableCell(withIdentifier: "eventCell", for: indexPath) as! EventTableViewCell
eventStoryboard.getEventName = events[indexPath.row].name ?? "nil"
self.navigationController?.pushViewController(eventStoryboard, animated: false) }
How to solve this issue and send filtered correct data to new view controller?
Thanks in advance.

Issue trying to complete Firebase Storage download before showing tableview

I have a table view where depending on the cell class it will download an image from Firebase. I've noticed when using the app that cells with the same cell identifier will show the previous downloaded image before showing the new one. This is what I have before changing it.
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if tableData[indexPath.row]["Image"] != nil {
let cell = tableView.dequeueReusableCell(withIdentifier: "imageNotesData", for: indexPath) as! ImageNotesCell
cell.notes.delegate = self
cell.notes.tag = indexPath.row
cell.notes.text = tableData[indexPath.row]["Notes"] as! String
guard let imageFirebasePath = tableData[indexPath.row]["Image"] else {
return cell }
let pathReference = Storage.storage().reference(withPath: imageFirebasePath as! String)
pathReference.getData(maxSize: 1 * 1614 * 1614) { data, error in
if let error = error {
print(error)
} else {
let image = UIImage(data: data!)
cell.storedImage.image = image
}
}
return cell
}
else {
let cell = tableView.dequeueReusableCell(withIdentifier: "notesData", for: indexPath) as! NotesCell
//let noteString = tableData[indexPath.row]["Notes"] as! String
cell.notes.text = tableData[indexPath.row]["Notes"] as! String
cell.notes.delegate = self
cell.notes.tag = indexPath.row
return cell
}
}
Knowing that this is not a good user experience and that it looks clunky, I tried to move the pathReference.getData to where I setup the data but the view appears before my images finish downloading. I have tried to use a completion handler but I'm still having issues.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
getSectionData(userID: userID, city: selectedCity, completion: {(sectionString) in
self.setupTableCellView(userID: userID, city: selectedCity, section: sectionString) { (tableData) in
DispatchQueue.main.async(execute: {
self.cityName?.text = selectedCity
self.changeSections.setTitle(sectionString, for: .normal)
self.currentSectionString = sectionString
self.setupTableData(tableDataHolder: tableData)
})
}
})
}
func setupTableCellView(userID: String, city: String, section: String, completion: #escaping ([[String:Any]]) -> () ) {
let databaseRef = Database.database().reference().child("Users").child(userID).child("Cities").child(city).child(section)
var indexData = [String:Any]()
var indexDataArray = [[String:Any]]()
databaseRef.observeSingleEvent(of: .value, with: { (snapshot) in
for dataSet in snapshot.children {
let snap = dataSet as! DataSnapshot
//let k = snap.key
let v = snap.value
indexData = [:]
for (key, value) in v as! [String: Any] {
//indexData[key] = value
if key == "Image" {
//let pathReference = Storage.storage().reference(withPath: value as! String)
print("before getImageData call")
self.getImageData(pathRef: value as! String, completion: {(someData) in
print("before assigning indexData[key]")
indexData[key] = someData
print("after assigning indexData[key]")
})
} else {
indexData[key] = value
}
}
indexDataArray.append(indexData)
}
completion(indexDataArray)
})
}
func getImageData(pathRef: String, completion: #escaping(UIImage) -> ()) {
let pathReference = Storage.storage().reference(withPath: pathRef as! String)
pathReference.getData(maxSize: 1 * 1614 * 1614, completion: { (data, error) in
if let error = error {
print(error)
} else {
let image = UIImage(data:data!)
print("called before completion handler w/ image")
completion(image!)
}
})
}
I don't know if I am approaching this the right way but I think I am. I'm also guessing that the getData call is async and that is why it will always download after showing the table view.
You can't do this.
Make the request from Firebase.
Over time, you will get many replies - all the information and all the changing information.
When each new item arrives - and don't forget it may be either an addition or deletion - alter your table so that it displays all the current items.
That's OCC!
OCC is "occasionally connected computing". A similar phrase is "offline first computing". So, whenever you use any major service you use every day like Facebook, Snapchat, etc that is "OCC": everything stays in sync properly whether you do or don't have bandwidth. You know? The current major paradigm of device-cloud computing.
Edit - See Fattie's comments about prepareForReuse()!
With reusable table cells, the cells will at first have the appearance they do by default / on the xib. Once they're "used", they have whatever data they were set to. This can result in some wonky behavior. I discovered an issue where in my "default" case from my data, I didn't do anything ecause it already matched the xib, but if the data's attributes were different, I updated the appearance. The result was that scrolling up and down really fast, some things that should have had the default appearance had the changed appearance.
One basic solution to just not show the previous image would be to show a place holder / empty image, then call your asynchronous fetch of the image. Not exactly what you want because the cell will still show up empty...
Make sure you have a local store for the images, otherwise you're going to be making a server request for images you already have as you scroll up and down!
I'd recommend in your viewDidLoad, call a method to fetch all of your images at once, then, once you have them all, in your success handler, call self.tableview.reloadData() to display it all.

ios - Setting value in to FIRDataSnapshot

I'm new to swift and having trouble with setting value to FIRDataSnapshot. I simply created a calculator. I took MealCaloryArray in didload method and display it tableviewcell (with the help of FIRDataSnapshot list) and the calory is changed in the plus function and I have to send the new value to tableviewcell again. However, I couldnt set the new value in FIRDataSnapshot array list. I tried to useself.calory[buttonRow].setValue(<value: n, forUndefinedKey:"")but I dont have proper "forUndefinedKey" value. Do you have any suggestions?
My nested Firebase DB Structure and code blocks is attached.
Firebase Child Structure:
Database Screenshot
var calory: [FIRDataSnapshot]! = []
override func viewDidLoad() {
ref = FIRDatabase.database().reference()
let CoursesRef = ref.child("CompanyMeals")
CoursesRef.observe(.childAdded, with: { snapshot in
self.calory = snapshot.childSnapshot(forPath: "MealCaloryArray").children.allObjects as! [FIRDataSnapshot]
self.calory.append(snapshot)
self.ingredientTableView.reloadData()
})
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = ingredientTableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! MealCalculatorListCell
let cellcalory = self.calory[indexPath.row].value as? Double
if (cellcalory != nil) {
cell.itemTotalCalory.text = ("\(cellcalory!)")//String (describing: cellcalory)
let cellcalory1 = Int(cellcalory!)
firstCaloriesArray.append((cellcalory1 as AnyObject))
}
}
#IBAction func plusAction(sender: UIButton) {
cell.itemTotalCalory.text = String ((Int(oldcalory!) + fcCalory))
let newcalory = cell.itemTotalCalory.text
let n = String(newcalory!)
self.calory[buttonRow].setValue(value: n, forUndefinedKey: "")
}

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