How to pass sequential data into a navigationBarTitle in SwiftUI - swiftui

Question

I have a master-detail app that starts with a list of Users -> Their Cities -> Their Towns. The content of the views is working fine, but I can't figure out how to adjust my data flow so that the .navigationBarTitle reflects the previously selected item. e.g. if I pick user "jimmy" I want "jimmy" to be the title over the list of cities.
Here is my data model:
import SwiftUI
struct UserModel: Codable, Identifiable {
let id: Int
let firstName: String
let lastName: String
let cities: [CityModel]
enum CodingKeys: String, CodingKey {
case id
case firstName = "first_name"
case lastName = "last_name"
case cities
}
}
struct CityModel: Codable, Identifiable {
let id: Int
let name: String
let towns: [TownModel]
}
struct TownModel: Codable, Identifiable {
let id: Int
let name: String
}
Here is my root view, UserList.swift:
import SwiftUI
struct UserList: View {
var body: some View {
NavigationView {
List(userData) { user in
NavigationLink(destination: CityList(cities: user.cities)) {
UserRow(user: user)
}
}
.navigationBarTitle(Text("Users"))
}
}
}
struct UserList_Previews: PreviewProvider {
static var previews: some View {
UserList()
}
}
And here is the CityList.swift clicking a user is opening:
import SwiftUI
struct CityList: View {
var thisUser: UserModel
var cities: [CityModel]
var body: some View {
List (cities) { city in
NavigationLink(destination: TownList(towns: city.towns)) {
CityRow(city: city)
}.navigationBarTitle(Text(self.thisUser.firstName))
}
}
}
The error is thrown on the following line of UserList.swift, because it's calling to CityList but isn't account for CityList's reference of "thisUser". Only I'm not sure what the correct syntax is to adjust it.
NavigationLink(destination: CityList(cities: user.cities)) { UserRow(user: user) }
ERROR: Missing argument for parameter 'thisUser' in call
Any help is much appreciated.

Answer 1

You can pass the user to CityList just as you passed the list of cities.
The error message is telling you that you're missing one of the parameters for the memberwise initializer that CityList automatically receives. The memberwise initializer takes all of the struct's properties and, I believe, in the order in which they're declared in the struct.
NavigationLink(destination: CityList(thisUser: user, cities: user.cities)) { UserRow(user: user) }