#EnvironmentVariable not being passed to child views - swiftui

Question

I have 2 views - which I want to navigate between, and have a viewModel object shared between them as an EnvironmentObject. I keep getting the "A View.environmentObject(_:) for TidesViewModel may be missing as an ancestor of this view." error - but none of the solutions I have found seem to work. Please find below my code. The following is the first view:
import SwiftUI
struct ContentView: View {
#ObservedObject var tidesViewModel: TidesViewModel = TidesViewModel()
var body: some View {
NavigationView
{
List
{
ForEach (tidesViewModel.stations.indices) {
stationid in
HStack
{
NavigationLink(destination: TideDataView(stationId: tidesViewModel.stations[stationid].properties.Id))
{
Text(tidesViewModel.stations[stationid].properties.Name)
}
}
}
}
}.environmentObject(tidesViewModel)
}
}
and below is the child view - which throws the error.
import SwiftUI
struct TideDataView: View {
#EnvironmentObject var tidesViewModel : TidesViewModel
var stationId: String
init(stationId: String) {
self.stationId = stationId
getTidesForStation(stationId: stationId)
}
var body: some View {
List
{
ForEach (tidesViewModel.tides.indices)
{
tideIndex in
Text(tidesViewModel.tides[tideIndex].EventType)
}
}
}
func getTidesForStation(stationId: String)
{
tidesViewModel.getTidalData(forStation: stationId)
}
}
For completeness - below is the Observable object being passed:
import Foundation
import SwiftUI
class TidesViewModel: ObservableObject
{
private var tideModel: TideModel = TideModel()
var currentStation: Feature?
init()
{
readStations()
}
var stations: [Feature]
{
tideModel.features
}
var tides: [TidalEvent]
{
tideModel.tides
}
func readStations()
{
let stationsData = readLocalFile(forName: "stations")
parseStations(jsonData: stationsData!)
}
private func readLocalFile(forName name: String) -> Data? {
do {
if let bundlePath = Bundle.main.path(forResource: name,
ofType: "json"),
let jsonData = try String(contentsOfFile: bundlePath).data(using: .utf8) {
return jsonData
}
} catch {
print(error)
}
return nil
}
private func parseStations(jsonData: Data) {
do {
let decodedData: FeatureCollection = try JSONDecoder().decode(FeatureCollection.self,
from: jsonData)
//print(decodedData)
tideModel.features = decodedData.features
} catch let jsonError as NSError{
print(jsonError.userInfo)
}
}
func getTidalData(forStation stationId: String)
{
let token = "f43c068141bb417fb88909be5f68781b"
guard let url = URL(string: "https://admiraltyapi.azure-api.net/uktidalapi/api/V1/Stations/" + stationId + "/TidalEvents") else {
fatalError("Invalid URL")
}
var request = URLRequest(url: url)
request.httpMethod = "GET"
request.setValue(token, forHTTPHeaderField: "Ocp-Apim-Subscription-Key")
URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else{ return }
do{
let decoder = JSONDecoder()
decoder.dataDecodingStrategy = .base64
let decodedData = try decoder.decode([TidalEvent].self, from: data)
DispatchQueue.main.async {
self.tideModel.tides = decodedData
}
}catch let error{
print(error)
}
}.resume()
}
}

Answer 1

You need to attach the modifier .environmentObject() directly to the view that will receive it. So, in your case, attach it to TideDataView, not to the NavigationView around it.
Your code would look like this:
NavigationLink {
TideDataView(stationId: tidesViewModel.stations[stationid].properties.Id)
.environmentObject(tidesViewModel)
} label: {
Text(tidesViewModel.stations[stationid].properties.Name)
}
// Delete the modifier .environmentObject() attached to the NavigationView