View not being updated when ViewModel gets new data - ios

Question

I have an app that will make an API call once a day to retrieve new data.
When the app launches it will check if new data is available, save new data to core data, call core data to show data in a view.
Issue
After saving new data to core data my view will not display the newly save data, but instead display the default dummy data from my model. The new data will be displayed after relaunching the app.
Question
How can I display the newly save data in the view without having to relaunch the app? I'm using MVVM pattern. Below is my code with links to my code.
UVIndexNowModel
class UVIndexNowModel: ObservableObject
{
#Published var uvIndex: Int
#Published var dateTime: Date
init(uvIndex: Int = 0, dateTime: Date = Date())
{
self.uvIndex = uvIndex
self.dateTime = dateTime
}
}
UVIndexNowViewModel
class UVIndexNowViewModel: NSObject, ObservableObject
{
private var isFirstAppearance = true
private let moc = PersistentStore.shared.context
private let nowController: NSFetchedResultsController<UVHour>
#Published var data: UVIndexNowModel = UVIndexNowModel()
#Published var coreDateError: Bool = false
override init()
{
nowController = NSFetchedResultsController(fetchRequest: UVHour.uvIndexNowRequest,
managedObjectContext: moc,
sectionNameKeyPath: nil, cacheName: nil)
super.init()
nowController.delegate = self
do {
try nowController.performFetch()
let results = nowController.fetchedObjects ?? []
setUVIndex(from: results)
} catch {
print("failed to fetch items!")
}
}
func setUVIndex(from hours: [UVHour])
{
let date = Date()
let formatter = DateFormatter()
formatter.timeZone = .current
formatter.dateFormat = "MMM/d/yyyy hh a"
let todaystr = formatter.string(from: date)
print("UVIndexNowVM.setUVIndex() size of UVHour array: \(hours.count)")
for i in hours
{
let tempDateStr = formatter.string(from: i.wrappedDateTime)
if todaystr == tempDateStr
{
print("UV Now VM Date matches! \(tempDateStr)")
self.data.uvIndex = i.wrappedUVIndex
self.data.dateTime = i.wrappedDateTime
break
}
}
}
}
extension UVIndexNowViewModel: NSFetchedResultsControllerDelegate
{
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)
{
print("UVIndexNowViewModel controllerDidChangeContent was called. New Stuff in DB")
guard let results = controller.fetchedObjects as? [UVHour] else { return }
setUVIndex(from: results)
}
}
UVIndexNowView
struct UVIndexNowView: View {
#ObservedObject var vm = UVIndexNowViewModel()
var body: some View {
VStack {
Text("\(vm.data.dateTime)")
Text("UV Index: \(vm.data.uvIndex)")
}
}
}

Answer 1

As your UVIndexNowModel is-a ObservableObject you need to observe it in separated view, like
struct UVIndexNowView: View {
#ObservedObject var vm = UVIndexNowViewModel()
var body: some View {
UVIndexNowDataView(data: vm.data) // << here !!
}
}
and
struct UVIndexNowDataView: View {
#ObservedObject var data: UVIndexNowModel
var body: some View {
VStack {
Text("\(data.dateTime)")
Text("UV Index: \(data.uvIndex)")
}
}
}