How do I load data using ObservableObject in SwiftUI? - amazon-dynamodb

I am trying to transition an app from UIKit to SwiftUI which depends on basic DynamoDB resources but I have hit a snag in forcing the view to refresh as data is added to the list. I have been at this set of code for hours trying different things and I thought I might see if anyone might know why the 'SessionsData' seems to be thrown away and will not accumulate the 'Sessions' objects.
Does anyone have any quick thoughts???
class SessionsData: ObservableObject {
let didChange = PassthroughSubject<SessionsData, Never>()
#Published var data: [Sessions] = [] {
didSet {
didChange.send(self)
}
}
init() {
load()
}
func load() {
let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.default()
let scanExpression = AWSDynamoDBScanExpression()
scanExpression.limit = 20
var temp : [Sessions] = []
dynamoDBObjectMapper.scan(Sessions.self, expression: scanExpression).continueWith(block: { (task:AWSTask<AWSDynamoDBPaginatedOutput>!) -> Any? in
if let error = task.error as NSError? {
print("The request failed. Error: \(error)")
} else if let paginatedOutput = task.result {
for session in paginatedOutput.items as! [Sessions] {
print("Item Found")
temp.append(session)
}
DispatchQueue.main.async {
self.data = temp
self.didChange.send(self)
}
}
print(self.data.count)
return true
})
}
}
struct Events: View {
#ObservedObject var sessionsData = SessionsData()
var body: some View {...}
}

Looks like you've over-complicated the code. The PassthroughSubject is unnecessary. Whenever you change a #Published property, it should trigger an update.
class SessionsData: ObservableObject {
#Published var data: [Sessions] = []
init() {
load()
}
func load() {
let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.default()
let scanExpression = AWSDynamoDBScanExpression()
scanExpression.limit = 20
var temp : [Sessions] = []
dynamoDBObjectMapper.scan(Sessions.self, expression: scanExpression).continueWith(block: { (task:AWSTask<AWSDynamoDBPaginatedOutput>!) -> Any? in
if let error = task.error as NSError? {
print("The request failed. Error: \(error)")
} else if let paginatedOutput = task.result {
for session in paginatedOutput.items as! [Sessions] {
print("Item Found")
temp.append(session)
}
DispatchQueue.main.async {
self.data = temp
}
}
print(self.data.count)
return true
})
}
}

I don't have experience with DynamoDB, but here are a few things from SwiftUI / Combine perspective. In ObseravbleObjects have change a significant bit and and are now declared with objectWillChange and then sending newValue in willSet:
class SessionsData: ObservableObject {
public let objectWillChange = PassthroughSubject<[Sessions], Never>()
public private(set) var items: [Sessions] = [] {
willSet {
objectWillChange.send(newValue)
}
}
init() {
self.items = []
}
public func load() {
let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.default()
let scanExpression = AWSDynamoDBScanExpression()
scanExpression.limit = 20
var temp: [Sessions] = []
dynamoDBObjectMapper
.scan(Sessions.self,
expression: scanExpression)
.continueWith(block: { (task:AWSTask<AWSDynamoDBPaginatedOutput>!) -> Any? in
if let error = task.error as NSError? {
print("The request failed. Error: \(error)")
} else if let paginatedOutput = task.result,
let sessions = paginatedOutput.items as? [Sessions] {
temp.append(contentsOf: sessions)
}
DispatchQueue.main.async {
self.items = temp
}
}
return true
})
}
}
For the UI part you have to just call your load() method defined above in .onApear() and everything else should happen magically:
struct Events: View {
#ObservedObject var sessionsData: SessionsData
var body: some View {
List {
ForEach(self.sessionsData.items) { session in
Text(session.name) // or something of that kind
}
} .onAppear(perform: { self.sessionsData.load() })
}
}

Related

Access Data from Firestore and Put it in SwiftUI EnvironmentObject

I am trying to use Firestore and get the data from the Firestore and then put it in EnvironmentObject. But it is not working out. I tried different approaches each ended with different errors.
Here is my code:
class FirebaseManager: ObservableObject {
#Published var tweets: [Tweet] = []
private let db: Firestore = Firestore.firestore()
init() {
db.collection("tweets")
.addSnapshotListener { snapshot, error in
if let error {
print(error.localizedDescription)
return
}
let tweets = snapshot?.documents.compactMap({ document in
try? document.data(as: Tweet.self)
})
if let tweets {
DispatchQueue.main.async {
self.tweets = tweets
}
}
}
}
}
Then I try to call FirebaseManager in the code below:
struct HomeTimelineScreen: View {
#EnvironmentObject var appState: AppState
#StateObject private var firebaseManager = FirebaseManager()
private var cancellables = Set<AnyCancellable>()
init() {
// ERROR Escaping closure captures mutating 'self' parameter
firebaseManager.$tweets.sink { tweets in
appState.tweets = tweets
}
// ERROR/WARNING ObservableObject of type AppState found. A View.environmentObject(_:) for AppState may be missing as an ancestor of this view.
firebaseManager.$tweets.assign(to: \.appState.tweets, on: self)
.store(in: &cancellables)
}
The EnvironmentObject AppState is injected in the TwitterApp main file as shown below:
#main
struct TwitterAppApp: App {
#ObservedObject var coordinator = Coordinator()
init() {
FirebaseApp.configure()
}
var body: some Scene {
WindowGroup {
NavigationStack(path: $coordinator.path) {
LandingScreen()
.navigationDestination(for: Route.self) { route in
switch route {
case .login:
LoginScreen().appLogoToolbar()
case .register:
RegistrationScreen().appLogoToolbar()
case .home:
HomeScreen()
case .detail(let tweet):
TweetDetailsScreen(tweet: tweet)
}
}
}.environmentObject(coordinator)
.environmentObject(AppState())
}
}
}
AppState:
import Foundation
class AppState: ObservableObject {
#Published var tweets: [Tweet] = []
}
UPDATE: My biggest issue is on how to re-render the TweetDetailScreen since it is also using the TweetCellView.
struct TweetDetailsScreen: View {
let tweet: Tweet
var body: some View {
List {
TweetCellView(tweet: tweet)
ForEach(1...20, id: \.self) { index in
Text("\(index)")
}
}
}
}
I took your advice and added single source of truth FirebaseManager and now it works as I want it to be.
struct TweetDetailsScreen: View {
#EnvironmentObject var firebaseManager: FirebaseManager
let tweet: Tweet
var body: some View {
List {
if let tweet = firebaseManager.findByDocumentId(tweet.documentID ?? "") {
TweetCellView(tweet: tweet)
}
ForEach(1...20, id: \.self) { index in
Text("\(index)")
}
}
}
}
class FirebaseManager: ObservableObject {
#Published var tweets: [Tweet] = []
private let db: Firestore = Firestore.firestore()
init() {
db.collection("tweets")
.addSnapshotListener { snapshot, error in
if let error {
print(error.localizedDescription)
return
}
let tweets = snapshot?.documents.compactMap({ document in
try? document.data(as: Tweet.self)
})
if let tweets {
DispatchQueue.main.async {
self.tweets = tweets
}
}
}
}
func findByDocumentId(_ documentId: String) -> Tweet? {
guard let index = tweets.firstIndex(where: { $0.documentID == documentId }) else { return nil }
return tweets[index]
}
}

Update toggle SwiftUI toggle switch with Firebase

Despite the simplicity of the question I have not been able to find a satisfactory answer yet. I want to update toggle switches based on value in Firebase. I have added listeners but run into problems converting a Bool to Binding Bool, any help is appreciated.
struct oneSeqeuncer : Identifiable{
var id: String
var status: Bool
}
struct Sequencers: View {
#ObservedObject var seqModel = SequencerModel()
#State private var novaseq404A :Bool = true
#State private var novaseq404B :Bool = true
#State private var novaseq297A :Bool = true
#State private var novaseq297B :Bool = true
var body: some View {
ZStack{
VStack{
Text("Sequencers")
.foregroundColor(.white)
.font(.title)
.fontWeight(.bold)
.padding()
List{
HStack{
Text("404")
.font(.title)
.padding()
Toggle("", isOn: $novaseq404A)
.onChange(of: novaseq404A) { newValue in
updateStatus(name: "404A", status: novaseq404A)
}
Toggle("", isOn: $novaseq404B)
.padding()
.onChange(of: novaseq404B) { newValue in
updateStatus(name: "404B", status: novaseq404B)
}
}
HStack{
Text("297")
.font(.title)
.padding()
Toggle("", isOn: $novaseq297A)
.onChange(of: novaseq297A) { newValue in
updateStatus(name: "297A", status: novaseq297A)
}
Toggle("", isOn: $novaseq297B)
.padding()
.onChange(of: novaseq297B) { newValue in
updateStatus(name: "297B", status: novaseq297B)
}
}
}
}
}.onAppear(){
self.seqModel.fetchData()
for seq in seqModel.seqs{
if seq.id == "404A"{
novaseq404A = seq.status
}
if seq.id == "404B"{
novaseq404A = seq.status
}
if seq.id == "297A"{
novaseq297A = seq.status
}
if seq.id == "297B"{
novaseq297B = seq.status
}
}
func updateStatus(name: String, status: Bool){
let timeInterval = NSDate().timeIntervalSince1970
let myInt = Int(timeInterval)
let db = Firestore.firestore()
if status == false{
db.collection("Sequencers").document(name).updateData([
"status": false,
"lastChange" : myInt
]){ error in
if error != nil{
print(error!)
}
}
}
else{
let docRef = db.collection("Sequencers").document(name)
docRef.getDocument {(document, error) in
if error != nil {
print(error!)
}
if let document = document, document.exists{
let data = document.data()
if let lastChange = data!["lastChange"]! as? Int{
let timeOff = myInt - lastChange
if let timeOffTotal = data!["timeOff"]! as? Int{
let newTimeOff = timeOffTotal + timeOff
db.collection("Sequencers").document(name).updateData([
"timeOff" : newTimeOff
])
}
}
db.collection("Sequencers").document(name).updateData([
"previousChange": data!["lastChange"]!,
"status": true ,
"lastChange" : myInt
])
}
}
}
}
}
struct Sequencers_Previews: PreviewProvider {
static var previews: some View {
Sequencers()
}
}
Below is my model for storing 'sequencers'
import Foundation
import FirebaseFirestore
import Firebase
class SequencerModel : ObservableObject {
#Published var seqs = [oneSeqeuncer]()
private var db = Firestore.firestore()
func fetchData(){
db.collection("Sequencers").addSnapshotListener { (querySnapshot, error) in
guard let documents = querySnapshot?.documents else {
print("No documents")
return
}
self.seqs = documents.map { queryDocumentSnapshot -> oneSeqeuncer in
let data = queryDocumentSnapshot.data()
let id = queryDocumentSnapshot.documentID
let status = data["status"] as? Bool
print(id)
print(status as Any)
return oneSeqeuncer(id: id, status: status!)
}
}
}
}
My solution was not ideal but solved, I realized the function .fetchData() that I was calling to was taking too long to respond. Ideally I should use some completion handler... However I simply changed my TabView on ContentView to display another page first, to allow time for my call to Firebase to finish, which allowed my for loop in .onAppear to have a non empty iterable. Again not sure this really belongs as an "Answer" but just wanted to share my temp solution as an option.

Generic parameter 'Success' could not be inferred; Key path value type '_' cannot be converted to contextual type '_'; Cannot find 'Response' in scope

I think this might be the last push for my project of mobile GitHub query repository search, but I get 3 errors I cannot find out how to cope with.
The code:
import SwiftUI
import Combine
struct Root: Codable {
let items: [Item]
enum CodingKeys: String, CodingKey {
case items
}
}
struct Item: Identifiable, Codable {
let id: Int
let urlCode: String
let fullName: String
enum CodingKeys: String, CodingKey {
case id
case urlCode = "url"
case fullName = "full_name"
}
}
private final class ContentViewState: ObservableObject {
#Published var isLoading = false
#Published var query = ""
#Published var stuff = [String]()
private var subscription: AnyCancellable?
func fetchRepos(query: String) {
isLoading = true
subscription = Just("test")
.delay(for: 2, scheduler: RunLoop.main)
.sink(receiveValue: {[weak self] (title: String) in
self?.isLoading = false
self?.stuff.append(title)
})
}
}
struct ContentView: View {
#StateObject private var state = ContentViewState()
#State private var items = [Item]()
var body: some View {
VStack {
if state.isLoading {
ProgressView()
} else {
HStack {
TextField("Enter search", text: $state.query)
Button("Search") {
state.fetchRepos(query: state.query)
}
}
List(items, id: \.id) { item in
VStack(alignment: .leading) {
Text(item.fullName).font(.headline)
Text(item.urlCode)
}
}.task {
await loadData()
}
}
}
}
func loadData() async {
guard let url = URL(string: "https://api.github.com/search/repositories?q=" + state.query + "&per_page=20") else
{
print("Invalid URL")
return
}
do {
let (data, _) = try await URLSession.shared.data(from: url)
if let decodedResponse = try? JSONDecoder().decode(Root.self, from: data) {
items = decodedResponse.items
}
} catch {
print("Invalid data ")
}
}
}
The errors:
"Generic parameter 'Success' could not be inferred" on line:
TextField("Enter search", text: $state.query)
"Key path value type '' cannot be converted to contextual type ''" on line:
await loadData()
}
}
"Cannot find 'Response' in scope" on line:
} catch {
print("Invalid data ")
}
}
}
Please help :)
The answer was to move the code to another file, change its structure a bit and everything works fine now!

How to chain ObservableObject?

I have a Game-object that may hold an image. Whenever an image URL is found for a game a new instance of GameImage-object should be created. It will then fetch the image and populate the UIImage property. When this happens the UI should be updated presenting the image.
class Game: ObservableObject {
#Published var image: GameImage?
}
class GameImage: ObservableObject {
let url: URL
#Published var image: UIImage?
private var cancellable: AnyCancellable?
init(url: URL) {
self.url = url
}
func fetch() {
self.cancellable = URLSession.shared.dataTaskPublisher(for: self.url)
.map { UIImage(data: $0.data) }
.replaceError(with: nil)
.receive(on: DispatchQueue.main)
.sink(receiveValue: { [weak self] (image) in
guard let self = self else { return }
self.image = image
print(self.url)
print(self.image)
})
}
func cancel() {
cancellable?.cancel()
}
deinit {
cancel()
}
}
struct ContentView: View {
#StateObject var game = Game()
var body: some View {
VStack {
if let image = game.image?.image {
Image(uiImage: image)
} else {
Text("No image.")
}
}
.onAppear(perform: {
guard let gameImageURL = URL(string: "https://cf.geekdo-images.com/itemrep/img/oVEpcbtyWkJjIjk1peTJo6hI1yk=/fit-in/246x300/pic4884996.jpg") else { return }
game.image = GameImage(url: gameImageURL)
game.image!.fetch()
})
}
}
The problem is. After fetch is done the debug console will show that image contains an UIImage. However the UI does not update to show the image. What am I missing here?
There is much more simpler solution than chaining ObservableObject, just separate dependent part into standalone subview... and all will work automatically.
Here is possible approach. Tested with Xcode 12 / iOS 14.
struct ContentView: View {
#StateObject var game = Game()
var body: some View {
VStack {
if nil != game.image {
GameImageView(vm: game.image!)
}
}
.onAppear(perform: {
guard let gameImageURL = URL(string: "https://cf.geekdo-images.com/itemrep/img/oVEpcbtyWkJjIjk1peTJo6hI1yk=/fit-in/246x300/pic4884996.jpg") else { return }
game.image = GameImage(url: gameImageURL)
game.image!.fetch()
})
}
}
struct GameImageView: View {
#ObservedObject var vm: GameImage
var body: some View {
if let image = vm.image {
Image(uiImage: image)
} else {
Text("No image.")
}
}
}

finding a nil value in session when accessing value in view

So i have a sessionStore:
class SessionStore: ObservableObject {
var handle: AuthStateDidChangeListenerHandle?
#Published var isLoggedIn = false
#Published var userInSession: User?
func listenAuthenticationState() {
handle = Auth.auth().addStateDidChangeListener({(auth, user) in
if let user = user {
let firestoreGetUser = Firestore.firestore().collection("users").document(user.uid)
firestoreGetUser.getDocument{(document, error) in
if let dict = document?.data() {
guard let decodedUser = try? User.init(fromDictionary: dict) else { return }
self.userInSession = decodedUser
print("decoded user = \(decodedUser)")
}
}
self.isLoggedIn = true
print("user logged in")
} else {
self.isLoggedIn = false
self.userInSession = nil
print("no one logged in")
}
})
}
func logout() {
do {
try Auth.auth().signOut()
} catch {
}
}
func unbind() {
if let handle = handle {
Auth.auth().removeStateDidChangeListener(handle)
}
}
deinit {
unbind()
}
}
Its working as expected, I am able to sign in etc.
I have the following to pull the current user data:
import Foundation
import Firebase
import FirebaseAuth
import FirebaseFirestore
class ProfileViewModel: ObservableObject {
var uid: String = ""
var email: String = ""
var username: String = ""
var profileURL: String = ""
var bio: String = ""
var occupation: String = ""
var city: String = ""
func LoadAUser(userId: String) {
Firestore.firestore().collection("users").document(userId).getDocument{(snapshot, error) in
guard let snap = snapshot else {
print("error fetching data")
return
}
let dict = snap.data()
guard let decodedUser = try? User.init(fromDictionary: dict!) else { return }
print("decoded user - load user - \(decodedUser)")
}
}
}
In my view im trying to call it like:
import SwiftUI
struct ProfileView: View {
#EnvironmentObject var session: SessionStore
#ObservedObject var profileViewModel = ProfileViewModel()
func loadUserData() {
profileViewModel.LoadAUser(userId: session.userInSession!.uid)
}
var body: some View {
VStack {
Text("Edit Profile")
.fontWeight(.semibold)
.font(.system(.title, design: .rounded))
.foregroundColor(Color("startColor"))
Spacer()
VStack(alignment: .leading) {
Text("view")
}.padding()
.onAppear(perform: loadUserData)
}
}
struct ProfileView_Previews: PreviewProvider {
static var previews: some View {
ProfileView()
}
}
Im using .onAppear(perform: loadUserData) which is causing an issue - Thread1: Fatal error: Unexpectedly found nil while unwrapping
I also tried:
init() {
profileViewModel.LoadAUser(userId: session.userInSession!.uid)
}
But this also causes the same error.
The thing is I should only be able to get to this view if I'm logged in as this already works:
struct InitialView: View {
#EnvironmentObject var session: SessionStore
func listen() {
session.listenAuthenticationState()
}
var body: some View {
Group {
if session.isLoggedIn {
MainView()
} else {
NavigationView {
SignUpView()
}
}
}.onAppear(perform: listen)
}
}
I have an initialView()
struct InitialView: View {
#EnvironmentObject var session: SessionStore
func listen() {
session.listenAuthenticationState()
}
var body: some View {
Group {
if session.isLoggedIn {
MainView()
} else {
NavigationView {
SignUpView()
}
}
}.onAppear(perform: listen)
}
}
which takes you to the MainView() which has tabs to control which screen you can navigate to, then from here i can go to ProfileView()
Anyway by the logic of provided code it is more correct to activate isLoggedIn in
let firestoreGetUser = Firestore.firestore().collection("users").document(user.uid)
firestoreGetUser.getDocument{(document, error) in
if let dict = document?.data() {
guard let decodedUser = try? User.init(fromDictionary: dict) else { return }
self.userInSession = decodedUser
print("decoded user = \(decodedUser)")
self.isLoggedIn = true // << here !!
print("user logged in")
}
}
So whats worked for me is passing in Auth instead of session data:
func loadUserData() {
profileViewModel.LoadAUser(userId: Auth.auth().currentUser!.uid)
}

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