In SwiftUI, I have a network request running in scenedelegate, scenedidbecomeactive. I don't know which view the user will be on when the app becomes active, but I want to present an alert if the data in the network request changes. I simplified the code below, so it's easy to read...
func sceneDidBecomeActive(_ scene: UIScene) {
let customClass = CustomClass()
customClass.performNetworkRequest()
In CustomClass, i have...
func performNetWorkRequest() {
URLSession.shared.dataTask(with: url) { (data, response, error) in
if let d = data {
let response = try JSONDecoder().decode(DetailResponse.self, from: d)
DispatchQueue.main.async {
//Here is where I want to either present an alert, but I can't figure out how to.
//OR do i put a func in SceneDeletegate to present the alert on the window.rootviewcontroller and then just call that func from here?
}
Any help is much appreciated!
Paul has a point - here's a possible implementation:
// In CustomClass.swift
import Combine
class CustomClass : ObservableObject {
#Published var dataRecieved = PassthroughSubject<DetailResponse, Never>()
init() {
performNetWorkRequest()
}
func performNetWorkRequest() {
URLSession.shared.dataTask(with: url) { (data, response, error) in
let response = try JSONDecoder().decode(DetailResponse.self, from: data)
DispatchQueue.main.async {
self.dataRecieved.send(response)
}
}
.resume()
}
}
// In SomeView.swift
import SwiftUI
import Combine
struct ContentView: View {
#State var showAlert = false
var customClass = CustomClass()
var body: some View {
Text("Hello, World!")
.onReceive(customClass.dataRecieved) { _ in
self.showAlert = true
}
.alert(isPresented: $showAlert) {
// your alert
}
}
}
Notice I didn't mention the SceneDelegate in any of these - this approach (called MVVM) is more flexible, in my opinion - besides, the way it is set up, performNetWorkRequest() will be executed as soon as your view is initialized, anyway.
You can also tweak the PassthroughSubject - I didn't know if you needed the DetailResponse or not.
Hope this helped!
Edit:
I just reread your question and it seems that this implementation is at fault as you noted there was no way to know what view the user would be on in the case of a network change. In that case, you can feed the same instance of CustomClass in your SceneDelegate as an EnvironmentObject.
Related
I'm making an app with SwiftUI and UIkit, I use UIkit for the main app controller and navigation, and I use SwiftUI for app design.
The app works very well, but I'm worried about the memory leaks. This is because the ViewModels I use to pass data between views don't call desinit whene the view disappears. I know that in SwiftUI views are not disposed immediately, but since I'm using UIKit to navigate I don't know what the problem is.
//The ViewModel for each user fetched
internal class UserViewModel: ObservableObject, Identifiable {
//MARK: - Propeties var currentListener: ListenerRegistration?
#Published var request: Request?
#Published var user: User
init(user: User) {
self.user = user
getRequest()
fetchAdmins()
}
deinit {
//Dosnt get called removeListener()
}
func getRequest() {
guard let uid = Auth.auth().currentUser?.uid else {return}
guard let id = id else {return}
self.currentListener = Collections.requests(id).document(uid).addSnapshotListener { snapshot, error in
if let error = error {
print(error.localizedDescription)
return
}
if ((snapshot?.exists) != nil) {
if let request = try? snapshot!.data(as: Request.self) {
DispatchQueue.main.async {
self.request = request
}
}
}
}
}
func removeListener() {
self.currentListener?.remove()
}
}
}
//The ViewModel to fetch all the users ViewModels
class UsersViewModel: ObservableObject {
#Published var users = [UserViewModel]()
func fetch() {
DispatchQueue.global(qos: .background).async {
Collections.users.getDocuments(completion: { snapshot, err in
guard let documents = snapshot?.documents else { return } let users = documents.compactMap({ try? $0.data(as: User.self) })
users.forEach { user in
let vm = UserViewModel(user: user)
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
self.users.append(vm)
}
}
})
}
} }
//Show the users cells with the ViewModel
struct HomeView: View {
#ObservedObject var usersViewModels: UsersViewModel
//MARK: - Init
init() {
self.usersViewModels = UsersViewModel()
}
var body: some View {
ListView(content: {
ForEach(usersViewModels) { usersViewModel in
UserCell(viewModel: usersViewModel).id(user.id)
}
})
}
}
This is how I navigate between controllers and views of my app. I don't use NavigationLinks:
public static func push<Content: View>(view: Content) {
DispatchQueue.main.async {
guard let tabBarController = UIApplication.rootViewController as? UITabBarController, let navigationController = tabBarController.selectedViewController as? UINavigationController else { return nil }
if let navigationController = UIApplication.getCurrentNavigationController() {
navigationController.pushViewController(HostingController(content: view), animated: true)
}
}
}
Does anyone know if this method that I am using to navigate can cause me memory problems? And you know why my app doesn't reduce its memory every time I close a window, it just increases more and more.
The disappearing does not mean it is no longer in memory.
It looks like you keep pushing them onto the navigation stack which increases their retain count.
You've got a memory leak here:
struct HomeView: View {
#ObservedObject var usersViewModels: UsersViewModel
//MARK: - Init
init() {
self.usersViewModels = UsersViewModel() // here
}
View structs must not init objects because the View struct is recreated every state change thus the object is being constantly init.
SwiftUI is all about taking advantage of value semantics, try to use #State with value types (or group them in a struct) in the View struct for your view data.
Model data structs go in a singleton ObservableObject supplied to the Views using .environmentObject.
UPDATE at the bottom.
I have followed the UIKit section of this Apple iOS Dev Tutorial, up to and including the Saving New Reminders section. The tutorials provide full code for download at the beginning of each section.
But, I want to get FirebaseFirestore involved. I have some other Firestore projects that work, but I always thought that I was doing something not quite right, so I'm always looking for better examples to learn from.
This is how I found Peter Friese's 3-part YT series, "Build a To-Do list with Swift UI and Firebase". While I'm not using SwiftUI, I figured that the Firestore code should probably work with just a few changes, as he creates a Repository whose sole function is to interface between app and Firestore. No UI involved. So, following his example, I added a ReminderRepository.
It doesn't work, but I'm so close. The UITableView looks empty but I know that the records are being loaded.
Stepping through in the debugger, I see that the first time the numberOfRowsInSection is called, the data hasn't been loaded from the Firestore, so it returns 0. But, eventually the code does load the data. I can see each Reminder as it's being mapped and at the end, all documents are loaded into the reminderRepository.reminders property.
But I can't figure out how to get the loadData() to make the table reload later.
ReminderRepository.swift
class ReminderRepository {
let remindersCollection = Firestore.firestore()
.collection("reminders").order(by: "date")
var reminders = [Reminder]()
init() {
loadData()
}
func loadData() {
print ("loadData")
remindersCollection.addSnapshotListener { (querySnapshot, error) in
if let querySnapshot = querySnapshot {
self.reminders = querySnapshot.documents.compactMap { document in
do {
let reminder = try document.data(as: Reminder.self)
print ("loadData: ", reminder?.title ?? "Unknown")
return reminder
} catch {
print (error)
}
return nil
}
}
print ("loadData: ", self.reminders.count)
}
}
}
The only difference from the Apple code is that in the ListDataSource.swift file, I added:
var remindersRepository: ReminderRepository
override init() {
remindersRepository = ReminderRepository()
}
and all reminders references in that file have been changed to
remindersRepository.reminders.
Do I need to provide a callback for the init()? How? I'm still a little iffy on the matter.
UPDATE: Not a full credit solution, but getting closer.
I added two lines to ReminderListViewController.viewDidLoad() as well as the referenced function:
refreshControl = UIRefreshControl()
refreshControl?.addTarget(self, action: #selector(refreshTournaments(_:)), for: .valueChanged)
#objc
private func refreshTournaments(_ sender: Any) {
tableView.reloadData()
refreshControl?.endRefreshing()
}
Now, when staring at the initial blank table, I pull down from the top and it refreshes. Now, how can I make it do that automatically?
Firstly create some ReminderRepositoryDelegate protocol, that will handle communication between you Controller part (in your case ReminderListDataSource ) and your model part (in your case ReminderRepository ). Then load data by delegating controller after reminder is set. here are some steps:
creating delegate protocol.
protocol ReminderRepositoryDelegate: AnyObject {
func reloadYourData()
}
Conform ReminderListDataSource to delegate protocol:
class ReminderListDataSource: UITableViewDataSource, ReminderRepositoryDelegate {
func reloadYourData() {
self.tableView.reloadData()
}
}
Add delegate weak variable to ReminderRepository that will weakly hold your controller.
class ReminderRepository {
let remindersCollection = Firestore.firestore()
.collection("reminders").order(by: "date")
var reminders = [Reminder]()
weak var delegate: ReminderRepositoryDelegate?
init() {
loadData()
}
}
set ReminderListDataSource as a delegate when creating ReminderRepository
override init() {
remindersRepository = ReminderRepository()
remindersRepository.delegate = self
}
load data after reminder is set
func loadData() {
print ("loadData")
remindersCollection.addSnapshotListener { (querySnapshot, error) in
if let querySnapshot = querySnapshot {
self.reminders = querySnapshot.documents.compactMap { document in
do {
let reminder = try document.data(as: Reminder.self)
print ("loadData: ", reminder?.title ?? "Unknown")
delegate?.reloadYourData()
return reminder
} catch {
print (error)
}
return nil
}
}
print ("loadData: ", self.reminders.count)
}
}
Please try changing var reminders = [Reminder]() to
var reminders : [Reminder] = []{
didSet {
self.tableview.reloadData()
}
}
I try to decode weather api
this is my struct class weatherModal :
import Foundation
struct WeatherModel:Decodable{
var main:Main?
}
struct Main:Decodable {
var temp : Double?
var feels_like : Double?
var temp_min:Double?
var temp_max:Double?
var pressure , humidity: Int?
}
I am trying to learn protocols. So this is where a make api call manager class :
protocol WeatherManagerProtocol:AnyObject {
func weatherData(weatherData:WeatherModel)
}
class WeatherManager{
var weather : WeatherModel?
weak var delegate :WeatherManagerProtocol?
public func callWeather(city:String) {
let url = "http://api.openweathermap.org/data/2.5/weather?q=\(city)&appid=1234"
URLSession.shared.dataTask(with:URL(string: url)!) { (data, response, err) in
if err != nil {
print(err!.localizedDescription)
} else {
do {
self.weather = try JSONDecoder().decode(WeatherModel.self, from: data!)
self.delegate?.weatherData(weatherData: self.weather!)
} catch {
print(error.localizedDescription)
}
}
}.resume()
}
}
In my ViewController what I want to do is user write city name on textfield and If user clicked the process button print the information about weather.
class ViewController: UIViewController {
#IBOutlet weak var textField: UITextField!
var weatherManager = WeatherManager()
var data : WeatherModel?
override func viewDidLoad() {
super.viewDidLoad()
weatherManager.delegate = self
// Do any additional setup after loading the view.
}
#IBAction func processButtonClicked(_ sender: Any) {
if textField.text != "" {
weatherManager.callWeather(city: textField.text ?? "nil")
print(data?.main?.humidity) // it print nil
} else{
print("empty")
}
}
extension ViewController: WeatherManagerProtocol{
func weatherData(weatherData: WeatherModel) {
self.data = weatherData
print(self.data.main)
// in here I can show my data
}
}
When I clicked process button it always print nil. Why ? What am I doing wrong?
You seem not to understand how your own code is supposed to work. The whole idea of the protocol-and-delegate pattern you've set up is that the "signal" round-trips thru the weather manager on a path like this:
You (the ViewController) say weatherManager.callWeather
The weather manager does some networking.
The weather manager calls its own delegate's weatherData.
You (the ViewController) are that delegate, so your weatherData is called and that is where you can print.
So that is the signal path:
#IBAction func processButtonClicked(_ sender: Any) {
weatherManager.callWeather(city: textField.text ?? "nil") // < TO wm
}
func weatherData(weatherData: WeatherModel) { // < FROM wm
// can print `weatherData` here
}
You cannot short circuit this path by trying to print the weather data anywhere else. Stay on the path. You cannot turn this into a "linear" simple path; it is asynchronous.
If you do want it to look more like a "linear" simple path, use a completion handler instead of a delegate callback. That's what I do in my version of this same experiment, so my view controller code looks like this:
self.jsonTalker.fetchJSON(zip:self.currentZip) { result in
DispatchQueue.main.async {
// and now `result` contains the weather data, or an error
Even better, use the Combine framework (or wait until Swift 6 implements async/await).
You call to weatherManager.callWeather that start URLSession.shared.dataTask. the task is executed asynchronously, but callWeather return immediately. So, when you print data?.main?.humidity, the task did not finish yet, and data is still nil. After the task finish, you call weatherData and assign the response to data.
I have a project using SwiftUI that requires CloudKit sharing, but I'm unable to get the UICloudSharingController to play nice in a SwiftUI environment.
First Problem
A straight-forward wrap of UICloudSharingController using UIViewControllerRepresentable yields an endless spinner (see this). As has been done for other system controllers like UIActivityViewController, I wrapped the UICloudSharingController in a containing UIViewController like this:
struct CloudSharingController: UIViewControllerRepresentable {
#EnvironmentObject var store: CloudStore
#Binding var isShowing: Bool
func makeUIViewController(context: Context) -> CloudControllerHost {
let host = CloudControllerHost()
host.rootRecord = store.noteRecord
host.container = store.container
return host
}
func updateUIViewController(_ host: CloudControllerHost, context: Context) {
if isShowing, host.isPresented == false {
host.share()
}
}
}
final class CloudControllerHost: UIViewController {
var rootRecord: CKRecord? = nil
var container: CKContainer = .default()
var isPresented = false
func share() {
let sharingController = shareController
isPresented = true
present(sharingController, animated: true, completion: nil)
}
lazy var shareController: UICloudSharingController = {
let controller = UICloudSharingController { [weak self] controller, completion in
guard let self = self else { return completion(nil, nil, CloudError.controllerInvalidated) }
guard let record = self.rootRecord else { return completion(nil, nil, CloudError.missingNoteRecord) }
let share = CKShare(rootRecord: record)
let operation = CKModifyRecordsOperation(recordsToSave: [record, share], recordIDsToDelete: [])
operation.modifyRecordsCompletionBlock = { saved, _, error in
if let error = error {
return completion(nil, nil, error)
}
completion(share, self.container, nil)
}
self.container.privateCloudDatabase.add(operation)
}
controller.delegate = self
controller.popoverPresentationController?.sourceView = self.view
return controller
}()
}
This allows the controller to come up normally, but...
Second Problem
Tap the close button or swipe to dismiss and the controller will disappear, but there's no notification that it's been dismissed. The SwiftUI view's #State property that initiated presenting the controller is still true. There's no obvious method to detect dismissal of the modal. After some experimenting, I discovered the presenting controller is the original UIHostingController created in the SceneDelegate. With some hackery, you can inject an object that is referenced in a UIHostingController subclass into the CloudSharingController. This will let you detect the dismissal and set the #State property to false. However, all nav bar buttons no longer function after dismissing so you could only ever tap this thing once. The rest of the scene is completely functional, but buttons in the nav bar don't respond.
Third Problem
Even if you could get the UICloudSharingController to present and dismiss normally, tapping on any of the sharing methods (Messages, Mail, etc) makes the controller disappear with no animation and the controller for the sharing URL doesn't come up. No crash or console messages--it just disappears.
Demo
I made a quick and dirty project on GitHub to demonstrate the issue: CloudKitSharing. It just creates a single String and a CKRecord to represent it using CloudKit. The interface displays the String (a UUID) with a single nav bar button to share it:
The Plea
Is there any way to use UICloudSharingController in SwiftUI? Don't have the time to rebuild the project in UIKit or a custom sharing controller (I know--the price of being on the bleeding edge 💩)
I got this working -- initially, I wrapped the UICloudSharingController in a UIViewControllerRepresentable, much like the link you provided (I referenced that while building it), and simply adding it to a SwiftUI .sheet() view. This worked on the iPhone, but it failed on the iPad, because it requires you to set the popoverPresentationController?.sourceView, and I didn't have one, given that I triggered the sheet with a SwiftUI Button.
Going back to the drawing board, I rebuilt the button itself as a UIViewRepresentable, and was able to present the view using the rootViewController trick that SeungUn Ham suggested here. All works, on both iPhone and iPad - at least in the simulator.
My button:
struct UIKitCloudKitSharingButton: UIViewRepresentable {
typealias UIViewType = UIButton
#ObservedObject
var toShare: ObjectToShare
#State
var share: CKShare?
func makeUIView(context: UIViewRepresentableContext<UIKitCloudKitSharingButton>) -> UIButton {
let button = UIButton()
button.setImage(UIImage(systemName: "person.crop.circle.badge.plus"), for: .normal)
button.addTarget(context.coordinator, action: #selector(context.coordinator.pressed(_:)), for: .touchUpInside)
context.coordinator.button = button
return button
}
func updateUIView(_ uiView: UIButton, context: UIViewRepresentableContext<UIKitCloudKitSharingButton>) {
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
class Coordinator: NSObject, UICloudSharingControllerDelegate {
var button: UIButton?
func cloudSharingController(_ csc: UICloudSharingController, failedToSaveShareWithError error: Error) {
//Handle some errors here.
}
func itemTitle(for csc: UICloudSharingController) -> String? {
return parent.toShare.name
}
var parent: UIKitCloudKitSharingButton
init(_ parent: UIKitCloudKitSharingButton) {
self.parent = parent
}
#objc func pressed(_ sender: UIButton) {
//Pre-Create the CKShare record here, and assign to parent.share...
let sharingController = UICloudSharingController(share: share, container: myContainer)
sharingController.delegate = self
sharingController.availablePermissions = [.allowReadWrite]
if let button = self.button {
sharingController.popoverPresentationController?.sourceView = button
}
UIApplication.shared.windows.first?.rootViewController?.present(sharingController, animated: true)
}
}
}
Maybe just use rootViewController.
let window = UIApplication.shared.windows.filter { type(of: $0) == UIWindow.self }.first
window?.rootViewController?.present(sharingController, animated: true)
I'm writing a SwiftUI app, and I want it periodically refresh data from a server:
when the app is first opened
if the app enters the foreground and the data has not been updated in the past 5 minutes
Below is the code I have so far.
What is the best way to trigger this update code the first time the app is opened in a SwiftUI app? Is adding the observer in onAppear a good practice for triggering the update when the app enters the foreground? (This is the only view in the app)
class InfoStore {
var lastValueCheck: Date = .distantPast
}
struct ContentView : View {
var infoStore: InfoStore
private func updateValueFromServer() {
// request updated value from the server
// if the request is successful, store the new value
currentValue = 500
UserDefaults.cachedValue = 500
// hardcoded for this example
infoStore.lastValueCheck = Date()
}
private func updateValueIfOld() {
let fiveMinutesAgo: Date = Date(timeIntervalSinceNow: (-5 * 60))
if infoStore.lastValueCheck < fiveMinutesAgo {
updateValueFromServer()
}
}
#State var currentValue: Int = 100
var body: some View {
Text("\(currentValue)")
.font(.largeTitle)
.onAppear {
NotificationCenter.default.addObserver(forName: UIApplication.willEnterForegroundNotification,
object: nil,
queue: .main) { (notification) in
self.updateValueIfOld()
}
}
}
}
extension UserDefaults {
private struct Keys {
static let cachedValue = "cachedValue"
}
static var cachedValue: Int {
get {
return standard.value(forKey: Keys.cachedValue) as? Int ?? 0
}
set {
standard.set(newValue, forKey: Keys.cachedValue)
}
}
}
1) About the first point (app first opened): probably the best way to get what you want is to extract the logic outside the View (as MVVM suggests) using DataBinding and ObservableObjects. I changed your code as less as possible in order to show you what I mean:
import SwiftUI
class ViewModel: ObservableObject {
#Published var currentValue = -1
private var lastValueCheck = Date.distantPast
init() {
updateValueFromServer()
}
func updateValueIfOld() {
let fiveMinutesAgo: Date = Date(timeIntervalSinceNow: (-5 * 60))
if lastValueCheck < fiveMinutesAgo {
updateValueFromServer()
}
}
private func updateValueFromServer() {
// request updated value from the server
// if the request is successful, store the new value
currentValue = 500
UserDefaults.cachedValue = 500
// hardcoded for this example
lastValueCheck = Date()
}
}
struct ContentView : View {
#ObservedObject var viewModel: ViewModel
var body: some View {
Text("\(viewModel.currentValue)")
.font(.largeTitle)
.onAppear {
NotificationCenter.default.addObserver(forName: UIApplication.willEnterForegroundNotification,
object: nil,
queue: .main) { (notification) in
self.viewModel.updateValueIfOld()
}
}
}
}
extension UserDefaults {
private struct Keys {
static let cachedValue = "cachedValue"
}
static var cachedValue: Int {
get {
return standard.value(forKey: Keys.cachedValue) as? Int ?? 0
}
set {
standard.set(newValue, forKey: Keys.cachedValue)
}
}
}
#if DEBUG
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(viewModel: ViewModel())
}
}
#endif
This way, as soon as the ViewModel is created the currentValue is updated. Also, every time currentValue is changed by a server call the UI is automatically recreated for you. Note that you have to modify the sceneDelegate this way:
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
if let windowScene = scene as? UIWindowScene {
let window = UIWindow(windowScene: windowScene)
window.rootViewController = UIHostingController(rootView: ContentView(viewModel: ViewModel()))
self.window = window
window.makeKeyAndVisible()
}
}
2) About the second point (app enters foreground): you should be careful here because you're registering the observer multiple times (every time the onAppear is fired). Depending on your needs you should decide to:
remove the observer onDisappear (this is very frequent)
add the observer just one time checking if you have already added it.
In any case it's a good practice to implement the:
deinit {
}
method and eventually remove the observer.