triggering picker data based another picker selection using swiftui

I have two API's for country and continent data. I want to change the country data based on the continent selection. I have tried to use the picker to fetch the data respectively from API, but i'm not able to manipulate the country data as per the selected continent option. Please help me with this issue. I'm beginner in the swift coding, please excuse my terminology. Thank you.
I'm expecting to get State data options based on the Country selected.

This the body of the view:

import SwiftUI

struct ContentView: View {
    @StateObject private var ContinentView = ContinentListViewModel()
    @State private var isExpanded = false
    @State private var selected = "Asia"
    
    @StateObject private var CountryView = CountryViewModels()
    @State private var Expanding = false
    @State private var isselected = "india"
    var body: some View {
        VStack {
            Section{
                Form{
                    Picker("Country*", selection: $isselected) {
                        ForEach(CountryView.countries, id: \.id) {
                            countries in Text(countries.value).tag(countries.value)
                        }
                    }
                    .onAppear(perform: CountryView.fetchCountry)
                    Picker("Continent*", selection: $selected) {
                        ForEach(ContinentView.continents, id: \.id) {
                            continents in Text(continents.value).tag(continents.value)
                                .onTapGesture {
                                    self.selected = continents.value
                                    withAnimation {
                                        self.isExpanded.toggle()
                                    }
                                }
                        }
                    }
                    .onAppear(perform: ContinentView.loadData)
                }
            }
        }
        .padding()
    }
}

CountryViewModel:

import Foundation
import SwiftUI



struct CountryList: Hashable, Codable {
    let id: Int
    let value: String
}
class CountryViewModels: ObservableObject {
    
    @Published var countries: [CountryList] = []
    
    func fetchCountry() {
        
        guard let url = URL(string: "https://arvfsmmasterdatamicroservice.azurewebsites.net/api/MasterData/getCountriesByContinentId") else {
            return
        }
        
        
        let task = URLSession.shared.dataTask(with: url) { [weak self] data, _, error in
            guard let data = data, error == nil else {
                return
            }
            
            // convert to JSON
            do {
                let countries = try JSONDecoder().decode([CountryList].self, from: data)
                DispatchQueue.main.sync {
                    self?.countries = countries
                }
            }
            catch {
                print(error)
            }
        }
        task.resume()
    }
}

ContinentViewModel:

import Foundation
import SwiftUI



struct ContinentList: Hashable, Codable, Identifiable {
    let id: Int
    let value: String
}

class ContinentListViewModel: ObservableObject {
    @Published var continents: [ContinentList] = []
    @StateObject private var ContinentView = ContinentListViewModel()
    func loadData() {
            guard let url = URL(string: "https://arvfsmmasterdatamicroservice.azurewebsites.net/api/MasterData/getContinents") else {
                return
            }
        
            let request = URLRequest(url: url)
            URLSession.shared.dataTask(with: request) { [weak self] data, continents, error in
                guard let data = data, error == nil else {
                    return
                }
                //convert to JSON
                do {
                    let continents = try JSONDecoder().decode([ContinentList].self, from: data)
                    DispatchQueue.main.async {
                        self?.continents = continents
                    }
                }
                catch {
                    print(error)
                }
            }.resume()
        }
}

I'm trying to connect the continent and country API to the picker, so when continent picker is selected it triggers the country API and view the list accordingly.

The core of your issue is that the URL for to retrieve the Countries needs the ContinentId

let url = "https://arvfsmmasterdatamicroservice.azurewebsites.net/api/MasterData/getCountriesByContinentId?continentId=\(continentId)"

To get to that you need to modify your code to be more representative and to connect to the different steps.

@State private var selectedContinent: ContinentModel? = nil

@State private var selectedCountry: CountryModel? = nil

This will make available all the data for the selected Continent/Country.

Then when the selected Continent changes get the new Country List.

.task(id: selectedContinent, {
    selectedCountry = nil
    countryVM.countries = []
    //Since a new continent was selected makes the selected country nil and empty the list
    guard let selectedContinent else { //Proceed if the continent isn't nil
        return
    }
    //Get the new countries list
    do {
        try await countryVM.fetchCountry(continentId: selectedContinent.id)
    } catch {
        //should display error.localizedDescription to user.
        print(error)
    }
})

Here is the full code, I made some other changes to account for errors and misrepresentations.

import SwiftUI

struct CountryPicker: View {
    @StateObject private var continentVM = ContinentListViewModel() //Variables should start with lowercase
    @State private var selectedContinent: ContinentModel? = nil
    
    @StateObject private var countryVM = CountryViewModels() //Variables should start with lowercase
    @State private var selectedCountry: CountryModel? = nil
    
    var body: some View {
        VStack {
            Section{
                Form{
                    Picker("Continent*", selection: $selectedContinent) {
                        Text("Select a Continent").tag(nil as ContinentModel?)
                        ForEach(continentVM.continents, id: \.id) {
                            continent in Text(continent.value).tag(continent as ContinentModel?)
                        }
                    }
                    .task {
                        do {
                            try await continentVM.loadData()
                        } catch {
                            //should display error.localizedDescription to user.
                            print(error)
                        }
                    }
                    Picker("Country*", selection: $selectedCountry) {
                        Text("Select a Country").tag(nil as CountryModel?)
                        ForEach(countryVM.countries, id: \.id) {
                            country in
                            Text(country.value).tag(country as CountryModel?)
                        }
                    }
                    .task(id: selectedContinent, { //This will run when the selected continent changes
                        selectedCountry = nil
                        countryVM.countries = []
                        //Since a new continent was selected makes the selected country nil and empty the list
                        guard let selectedContinent else { //Proceed if the continent isn't nil
                            return
                        }
                        //Get the new countries list
                        do {
                            try await countryVM.fetchCountry(continentId: selectedContinent.id)
                        } catch {
                            //should display error.localizedDescription to user.
                            print(error)
                        }
                    })
                }
            }
        }
        .padding()
    }
}

struct CountryModel: Hashable, Codable { //Rename to something that represents the object, this isnt a list it is a single object.
    let id: Int
    let value: String
}
class CountryViewModels: ObservableObject {
    
    @Published var countries: [CountryModel] = []
    
    func fetchCountry(continentId: Int) async throws {
        let url = "https://arvfsmmasterdatamicroservice.azurewebsites.net/api/MasterData/getCountriesByContinentId?continentId=\(continentId)"
        
        self.countries = try await URLSession.shared.decoded(url: url)
    }
}

struct ContinentModel: Hashable, Codable, Identifiable { //Rename to something that represents the object, this isnt a list it is a single object.
    let id: Int
    let value: String
}

class ContinentListViewModel: ObservableObject {
    @Published var continents: [ContinentModel] = []
    @StateObject private var ContinentView = ContinentListViewModel()
    func loadData() async throws {
        let url = "https://arvfsmmasterdatamicroservice.azurewebsites.net/api/MasterData/getContinents"
        
        self.continents = try await URLSession.shared.decoded(url: url)
    }
}

extension URLSession {
    func decoded<D>(url: String) async throws -> D where D: Decodable {
        guard let url = URL(string: url) else {
            throw URLError(.badURL)
        }
        let (data, response) = try await self.data(from: url)
        
        guard let httpsReponse = response as? HTTPURLResponse else {
            throw URLError(.badServerResponse)
        }
        
        guard httpsReponse.statusCode == 200 else { //Check the response, this accounts for network errors such as no web connection, web errors such as website unavailable, etc.
            throw URLError(URLError.Code(rawValue: httpsReponse.statusCode))
        }
        
        return try JSONDecoder().decode(D.self, from: data)
    }
}