If a property of my model object is an array of a custom object, how do I let users append objects to it? - ios

Question

I'm making an app where the user can create groups, and fill these groups with people. Groups are showed in a list and link to GroupViews, where there is a list of people part of that particular group.
The list of and creation of groups work as expected; the user can create groups and clicking any group takes the user to that specific groups own view.
The list of and creation of people don't work; when the user attempts to append a person to the people list it falls between the AddPersonView and GroupView and does not show up in the list.
Below is my current attempt at a solution:
Models.swift
import Foundation
struct Group: Identifiable {
var id: UUID
var name: String
var people: [Person]
init(name: String) {
self.id = UUID()
self.name = name
self.people = [Person]()
}
}
struct Person: Identifiable {
var id: UUID
var firstName: String
var lastName: String
}
ModelView.swift
import Foundation
class GroupList: ObservableObject {
#Published var groups = [Group]()
}
ContentView.swift
import SwiftUI
struct ContentView: View {
#ObservedObject var groupList: GroupList
#State private var showingAddGroupView = false
var body: some View {
NavigationView {
List(groupList.groups) { group in
NavigationLink(destination: GroupView(group: group.people)) {
Text(group.name)
}
}
.navigationBarItems(trailing:
Button(action: {
self.showingAddGroupView.toggle()
}) {
Text("Add group")
})
}
.sheet(isPresented: $showingAddGroupView) {
AddGroupView(groupList: self.groupList)
}
}
}
AddGroupView.swift
import SwiftUI
struct AddGroupView: View {
#Environment(\.presentationMode) var presentationMode
#ObservedObject var groupList: GroupList
#State private var name = ""
var body: some View {
VStack {
TextField("Name", text: self.$name)
Button(action: {
self.groupList.groups.append(Group(name: self.name))
self.presentationMode.wrappedValue.dismiss()
}) {
Text("OK")
}
}
}
}
GroupView.swift
import SwiftUI
struct GroupView: View {
var group: [Person]
#State private var showingAddPersonView = false
var body: some View {
NavigationView {
VStack {
List(group) { person in
NavigationLink(destination: Text(person.firstName)) {
Text("\(person.firstName) \(person.lastName)")
}
}
.sheet(isPresented: $showingAddPersonView) {
AddPersonView(group: self.group)
}
}
.navigationBarItems(trailing:
Button(action: {
self.showingAddPersonView.toggle()
}) {
Text("Add person")
})
}
}
}
AddPersonView.swift
import SwiftUI
struct AddPersonView: View {
#Environment(\.presentationMode) var presentationMode
#State var group: [Person]
#State private var firstName = ""
#State private var lastName = ""
var body: some View {
VStack {
TextField("First name", text: self.$firstName)
TextField("Last name", text: self.$lastName)
Button(action: {
self.group.append(Person(id: UUID(), firstName: self.firstName, lastName: self.lastName))
self.presentationMode.wrappedValue.dismiss()
}) {
Text("OK")
}
}
}
}

Answer 1

check this out:
the problem is exactly there what Lou said - structs will be copied. you must change and work on your observable object - not on copies.
import SwiftUI
import Foundation
struct Group: Identifiable {
var id: UUID
var name: String
var people: [Person]
init(name: String) {
self.id = UUID()
self.name = name
self.people = [Person]()
}
}
struct Person: Identifiable {
var id: UUID
var firstName: String
var lastName: String
}
class GroupList: ObservableObject {
#Published var groups = [Group]()
func getGroupBy(id: UUID) -> Group? {
let result = groups.filter { $0.id == id }
if result.count == 1 {
return result[0]
}
return nil
}
func getGroupIndex(id: UUID) -> Int? {
return groups.firstIndex { $0.id == id }
}
}
struct ContentView: View {
#EnvironmentObject var groupList: GroupList
#State private var showingAddGroupView = false
var body: some View {
NavigationView {
List(self.groupList.groups) { group in
NavigationLink(destination: GroupView(group: group).environmentObject(self.groupList)) {
Text(group.name)
}
}
.navigationBarItems(trailing:
Button(action: {
self.showingAddGroupView.toggle()
}) {
Text("Add group")
})
}
.sheet(isPresented: $showingAddGroupView) {
AddGroupView().environmentObject(self.groupList)
}
}
}
struct AddGroupView: View {
#Environment(\.presentationMode) var presentationMode
#EnvironmentObject var groupList: GroupList
#State private var name = ""
var body: some View {
VStack {
TextField("Name", text: self.$name)
Button(action: {
self.groupList.groups.append(Group(name: self.name))
self.presentationMode.wrappedValue.dismiss()
}) {
Text("OK")
}
}
}
}
struct GroupView: View {
#EnvironmentObject var groupList: GroupList
var group: Group
#State private var showingAddPersonView = false
var body: some View {
NavigationView {
VStack {
List(self.group.people) { person in
NavigationLink(destination: Text(person.firstName)) {
Text("\(person.firstName) \(person.lastName)")
}
}
.sheet(isPresented: $showingAddPersonView) {
AddPersonView(group: self.group).environmentObject(self.groupList)
}
}
.navigationBarItems(trailing:
Button(action: {
self.showingAddPersonView.toggle()
}) {
Text("Add person")
})
}
}
}
struct AddPersonView: View {
#Environment(\.presentationMode) var presentationMode
#EnvironmentObject var groupList : GroupList
#State var group: Group
#State private var firstName = ""
#State private var lastName = ""
var body: some View {
VStack {
TextField("First name", text: self.$firstName)
TextField("Last name", text: self.$lastName)
Button(action: {
if let index = self.groupList.getGroupIndex(id: self.group.id) {
self.groupList.groups[index].people.append(Person(id: UUID(), firstName: self.firstName, lastName: self.lastName))
self.group = self.groupList.groups[index]
}
self.presentationMode.wrappedValue.dismiss()
}) {
Text("OK")
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environmentObject(GroupList())
}
}

Answer 2

The issue is in GroupView, with this line
var group: [Person]
When you call AddPersonView, you are sending a copy of the array and the view appends a person to that copy and then it is lost when the view dismisses.
You must pass something that is shared. Probably this should all be in an ObservableObject and not local view variables.
Pass down the GroupList object or bindings to its internals