SwiftUI Data Flow Buggy Example

BuggyDataFlowContentView.swift

import SwiftUI

struct Person {
    let id: UUID
    var name: String
    var score: Float
}

class PersonStore: ObservableObject {
    @Published var people: [Person] = [
        .init(id: .init(), name: "Joe", score: 1),
        .init(id: .init(), name: "Jane", score: 5),
        .init(id: .init(), name: "John", score: 10)
    ]

    func add() {
        people.append(.init(id: .init(), name: "New Person", score: 0))
    }
}

struct ContentView: View {
    @EnvironmentObject var store: PersonStore

    var body: some View {
        NavigationView {
            List {
                ForEach(store.people.indexed(), id: \.1.id) { index, person in
                    NavigationLink(destination: EditView(person: self.$store.people[index])) {
                        RowView(person: person)
                    }
                }

                Button(action: store.add) {
                    Text("Add Person")
                }
            }
            .listStyle(SidebarListStyle())
        }
    }
}

struct RowView: View {
    let person: Person

    var body: some View {
        Text("\(person.name) (\(person.score))")
    }
}

struct EditView: View {
    @Binding var person: Person

    var body: some View {
        VStack {
            Text(person.name)
            Text("\(person.score)")
            TextField("Name", text: $person.name)
            Slider(value: $person.score, in: 0...100)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}

extension Sequence {
    func indexed() -> Array<(offset: Int, element: Element)> {
        return Array(enumerated())
    }
}