I have a DataBase handled by DataCore. I am trying to retrieve any object of "assignment" and insert it to a View List. The assignment class itself is identifiable but I am getting an error while trying to create the List in the View :
Initializer 'init(_:id:rowContent:)' requires that 'Set<NSManagedObject>' conform to 'RandomAccessCollection'
Is the set itself is not identifiable even though the objects are identifiable ? How can I present all the objects in the set inside the View's list ?
The view:
import SwiftUI
struct AssignmentList: View {
#ObservedObject var assignmentViewModel = assignmentViewModel()
var body: some View {
VStack {
NavigationView {
//**The error is in the following line : **
List(assignmentViewModel.allAssignments, id: \.self) { assignment in
AssignmentRow(assignmentName: assignment.assignmentName, notes: assignment.notes) //This view works by itself and just present the data as text under HStack
}
.navigationBarTitle(Text("Assignments"))
}
Button(action: {
self.assignmentViewModel.retrieveAllAssignments()
}) {
Text("Retrieve")
}
}
}
}
This is the assignment class:
import Foundation
import CoreData
extension Assignment: Identifiable {
#nonobjc public class func fetchRequest() -> NSFetchRequest<Assignment> {
return NSFetchRequest<Assignment>(entityName: "Assignment")
}
#NSManaged public var id: UUID?
#NSManaged public var assignmentName: String?
#NSManaged public var notes: String?
}
This is the ViewModel that connects to the view using binding:
class AssignmentViewModel : ObservableObject
{
private var assignmentModel = AssignmentModel()
/*AssignmentModel is a different class, we assume all methods working correctly and it's not a part of the question.*/
#Published var allAssignments : Set<Assignment>
init()
{
allAssignments=[]
}
func retrieveAllAssignment()
{
allAssignments=assignmentModel.retrieveAllAssignments()
}
}
Try the following
List(Array(assignmentViewModel.allAssignments), id: \.self) { assignment in
Related
How do I pass a bindable object into a view inside a ForEach loop?
Minimum reproducible code below.
class Person: Identifiable, ObservableObject {
let id: UUID = UUID()
#Published var healthy: Bool = true
}
class GroupOfPeople {
let people: [Person] = [Person(), Person(), Person()]
}
public struct GroupListView: View {
//MARK: Environment and StateObject properties
//MARK: State and Binding properties
//MARK: Other properties
let group: GroupOfPeople = GroupOfPeople()
//MARK: Body
public var body: some View {
ForEach(group.people) { person in
//ERROR: Cannot find '$person' in scope
PersonView(person: $person)
}
}
//MARK: Init
}
public struct PersonView: View {
//MARK: Environment and StateObject properties
//MARK: State and Binding properties
#Binding var person: Person
//MARK: Other properties
//MARK: Body
public var body: some View {
switch person.healthy {
case true:
Text("Healthy")
case false:
Text("Not Healthy")
}
}
//MARK: Init
init(person: Binding<Person>) {
self._person = person
}
}
The error I get is Cannot find '$person' in scope. I understand that the #Binding part of the variable is not in scope while the ForEach loop is executing. I'm looking for advice on a different pattern to accomplish #Binding objects to views in a List in SwiftUI.
The SwiftUI way would be something like this:
// struct instead of class
struct Person: Identifiable {
let id: UUID = UUID()
var healthy: Bool = true
}
// class publishing an array of Person
class GroupOfPeople: ObservableObject {
#Published var people: [Person] = [
Person(), Person(), Person()
]
}
struct GroupListView: View {
// instantiating the class
#StateObject var group: GroupOfPeople = GroupOfPeople()
var body: some View {
List {
// now you can use the $ init of ForEach
ForEach($group.people) { $person in
PersonView(person: $person)
}
}
}
}
struct PersonView: View {
#Binding var person: Person
var body: some View {
HStack {
// ternary instead of switch
Text(person.healthy ? "Healthy" : "Not Healthy")
Spacer()
// Button to change, so Binding makes some sense :)
Button("change") {
person.healthy.toggle()
}
}
}
}
You don't need Binding. You need ObservedObject.
for anyone still wondering... it looks like this has been added
.onContinuousHover(perform: { phase in
switch phase {
case .active(let location):
print(location.x)
case .ended:
print("ended")
}
})
I have viewmodel and view i have return some API logic in viewmodel and getting one dictionary after some logic..i want to access that dictionary value from view for ex.
viewmodel.someDic
but for now every-time i am getting empty dic.
class Viewmodel: ObservableObject {
#Published private var poductDetails:[String:ProductDetail] = [:]
func createItems(data: ProductRootClass) {
var productDetils = [String: SelectedProductDetail](){
//some logic
productDetils // with some object
self.poductDetails = productDetils
}
}
}
struct View: View {
#StateObject var viewModel: ViewModel
var body: some View {
VStack(alignment: .leading) {
Text("\(viewModel.poductDetails)")
}
.onAppear(perform: {
print("\(viewModel.poductDetails)")
})
}
}
I want to access this dictionary from view.
I tried accessing by returning productDetils from any function but get empty everytime.
may i know the way to access property from viewmodel to view?
You need a class conforming to ObservableObject and a property marked as #Published
class ViewModel : ObservableObject {
#Published var productDetails = [String:ProductDetail]()
func createItems(data: ProductRootClass) {
var productDetils = [String: SelectedProductDetail]()
//some logic
productDetils // with some object
self.productDetails = productDetils
}
}
Whenever the property is modified the view will be updated.
In the view create an instance and declare it as #StateObject
struct ContentView: View {
#StateObject var viewModel = ViewModel()
var body: some View {
VStack(alignment: .leading) {
ForEach(viewModel.productDetails.keys.sorted(), id: \.self) { key in
Text("\(viewModel.poductDetails[key]["someOtherKey"] as! String)")
}
}
}
}
I would prefer an array as model, it's easier to access
You need to get rid of the view model and make a proper model.
class Model: ObservableObject {
#Published private var productDetails:[ProductDetail] = []
}
struct ProductDetail: Identifiable {
let id = UUID()
var title: String
}
Now you can do ForEach(model.productDetails)
You can make your viewModel as a Singleton.
class ViewModel : ObservableObject {
static let viewModelSingleton = ViewModel()
#Published var productDetails = [String : ProductDetail]()
\\API logic}
Access this viewModel Singleton in the view
struct view : View {
#ObservedObject var viewModelObject = ViewModel.viewModelSingleton
var body: some View {
VStack(alignment: .leading) {
Text("\(viewModelObject.productDetails)")
}
}}
I can't create a binding with my 'username' property - Xcode gives me the error 'cannot find $social in scope'. Here is some of the essential code:
My problematic view:
struct ProfileSetter: View {
#Binding var profile: Profile
var body: some View {
ForEach(profile.socials, id: \.id) { social in
TextField(social.medium.rawValue, text: $social.username) //-> cannot find $social in scope
}
}
}
Its parent:
struct ProfileView: View {
#StateObject private var viewModel = ViewModel()
var body: some View {
ProfileSetter(profile: $viewModel.myProfile)
}
}
The simplified view model:
class ViewModel: ObservableObject {
#Published var myProfile = Profile(socials: [//multiple instances of Social])
}
And finally, the models:
struct Profile {
// other properties
var socials: [Social]
}
struct Social {
// other properties
var username: String
}
Replacing the text field with Text(social.username) works fine, so creating the binding seems to be the problem.
You cannot bind directly to value, you should do it via parent object, like
ForEach(profile.socials.indices, id: \.self) { index in
TextField(profile.socials[index].medium.rawValue,
text: $profile.socials[index].username)
}
Following this cheat sheet I'm trying to figure out data flow in SwiftUI. So:
Use #Binding when your view needs to mutate a property owned by an ancestor view, or owned by an observable object that an ancestor has a reference to.
And that is exactly what I need so my embedded model is:
class SimpleModel: Identifiable, ObservableObject {
#Published var values: [String] = []
init(values: [String] = []) {
self.values = values
}
}
and my View has two fields:
struct SimpleModelView: View {
#Binding var model: SimpleModel
#Binding var strings: [String]
var body: some View {
VStack {
HStack {
Text(self.strings[0])
TextField("name", text: self.$strings[0])
}
HStack {
Text(self.model.values[0])
EmbeddedView(strings: self.$model.values)
}
}
}
}
struct EmbeddedView: View {
#Binding var strings: [String]
var body: some View {
VStack {
TextField("name", text: self.$strings[0])
}
}
}
So I expect the view to change Text when change in input field will occur. And it's working for [String] but does not work for embedded #Binding object:
Why it's behaving differently?
Make property published
class SimpleModel: Identifiable, ObservableObject {
#Published var values: [String] = []
and model observed
struct SimpleModelView: View {
#ObservedObject var model: SimpleModel
Note: this in that direction - if you introduced ObservableObject then corresponding view should have ObservedObject wrapper to observe changes of that observable object's published properties.
In SimpleModelView, try changing:
#Binding var model: SimpleModel
to:
#ObservedObject var model: SimpleModel
#ObservedObjects provide binding values as well, and are required if you want state changes from classes conforming to ObservableObject
I am using SwiftUI on the Apple Watch and trying to use #ObservableObject, #ObservedObject, and #Binding correctly. I'm updating a value in a DetailView, and I want to have it reflected locally, as well as have the data changed globally. The code below works, but I am using a kludge to force the DetailView to redraw itself:
Is there a better way?
-------------- ContentView.swift ---------------
import Combine
import SwiftUI
struct person: Identifiable {
var id:Int = 0
var name:String
init( id: Int, name:String) {
self.id = id
self.name = name
}
}
class AppData: ObservableObject {
#Published var people:[person] = [person(id:0, name:"John"),
person(id:1, name:"Bret"),
person(id:2,name:"Sue"),
person(id:3,name:"Amy")]
}
var gAppData = AppData()
struct ContentView: View {
#ObservedObject var model:AppData
var body: some View {
List( model.people.indices ){ index in
NavigationLink(destination: DetailView(person:self.$model.people[index])) { Text(self.model.people[index].name) }
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(model:gAppData)
}
}
-------------- DetailView.swift ---------------
import SwiftUI
struct DetailView: View {
#Binding var person: person
// Created an unnecessary var to force a redreaw of the view
#State var doRedraw:Bool = true
var body: some View {
VStack(){
Text(person.name)
Button(action:{ self.person.name = "Bob"; self.doRedraw = false }) {
Text("Set Name to Bob")
}
}
}
}
struct DestView_Previews: PreviewProvider {
static var previews: some View {
DetailView(person:.constant(person( id:0, name:"John"))) // what does ".constant" actually do?
}
}
The problem here is because your view redraws only when you changes the #State or #Binding variable. Here you do not change the Person variable, but its property, which should not affect the user interface (because you didn't say to do this). I changed your code for a little for showing how to achieve this effect, you can go ahead from this point. You need to remember, what exactly affect UI:
class Person: Identifiable, ObservableObject { // better to assign struct/class names using UpperCamelCase
#Published var name:String // now change of this variable will affect UI
var id:Int = 0
init( id: Int, name:String) {
self.id = id
self.name = name
}
}
// changes in DetailView
struct DetailView: View {
#EnvironmentObject var person: Person
var body: some View {
VStack(){
Text(person.name)
Button(action:{ self.person.name = "Bob" }) {
Text("Set Name to Bob")
}
}
}
}
// preview
struct DetailViewWithoutGlobalVar_Previews: PreviewProvider {
static var previews: some View {
DetailView()
.environmentObject(Person(id: 1, name: "John"))
}
}
update: full code for List and Detail
import SwiftUI
class Person: Identifiable, ObservableObject { // better to assign type names using UpperCamelCase
#Published var name: String //{
var id: Int = 0
init( id: Int, name:String) {
self.id = id
self.name = name
}
func changeName(_ newName: String) {
self.name = newName
}
}
class AppData: ObservableObject {
#Published var people: [Person] = [Person(id:0, name:"John"),
Person(id:1, name:"Bret"),
Person(id:2,name:"Sue"),
Person(id:3,name:"Amy")]
}
struct ContentViewWithoutGlobalVar: View {
#EnvironmentObject var model: AppData
var body: some View {
NavigationView { // you forget something to navigate between views
List(model.people.indices) { index in
NavigationLink(destination: DetailView()
.environmentObject(self.model.people[index])) {
PersonRow(person: self.$model.people[index])
}
}
}
}
}
struct PersonRow: View {
#Binding var person: Person // this struct will see changes in Person and show them
var body: some View {
Text(person.name)
}
}
struct DetailView: View {
#EnvironmentObject var person: Person
var body: some View {
VStack(){
Text(self.person.name)
Button(action:{ self.person.changeName("Bob") }) {
Text("Set Name to Bob")
}
}
}
}
struct ContentViewWithoutGlobalVar_Previews: PreviewProvider {
static var previews: some View {
Group {
ContentViewWithoutGlobalVar()
.environmentObject(AppData())
DetailView()
.environmentObject(Person(id: 0, name: "John"))
}
}
}