I'm trying to create a Favorite list where I can add different items but it doesn't work. I made a simple code to show you what's going on.
// BookData gets data from Json
struct BookData: Codable {
var titolo: String
var descrizione: String
}
class FavoriteItems: ObservableObject {
#Published var favItems: [String] = []
}
struct ContentView: View {
#ObservedObject var bookData = BookDataLoader()
#ObservedObject var favoriteItems = FavoriteItems()
var body: some View {
NavigationView {
List {
NavigationLink(destination: FavoriteView()) {
Text("Go to favorites")
}
ForEach(0 ..< bookData.booksData.count) { num in
HStack {
Text("\(self.bookData.booksData[num].titolo)")
Button(action: {
self.favoriteItems.favItems.append(self.bookData.booksData[num].titolo)
}) {
Image(systemName: "heart")
}
}
}
}
}
}
}
struct FavoriteView: View {
#ObservedObject var favoriteItems = FavoriteItems()
var body: some View {
List {
ForEach (0 ..< favoriteItems.favItems.count) { num in
Text("\(self.favoriteItems.favItems[num])")
}
}
}
}
When I launch the app I can go to the Favorite View but after adding an Item I cannot.
My aim is to add an Item to Favorites and be able to save it once I close the app
The view model favoriteItems inside ContentView needs to be passed into FavoriteView because you need a reference of favoriteItems to reload FavoriteView when you add a new data.
Change to
NavigationView(destination: FavoriteView(favoriteItems: favoriteItems)) #ObservedObject var favoriteItems: FavoriteItems
It will be fine.
Thanks, X_X
Related
So I'm still learning Swift and I wanted to cleanup some code and break down views, but I can't seem to figure out how to pass data between views, so I wanted to reach out and check with others.
So let's say that I have MainView() which previously had this:
struct MainView: View {
#ObservedObject var model: MainViewModel
if let item = model.selectedItem {
HStack(alignment: .center, spacing: 3) {
Text(item.title)
}
}
}
Now I created a SecondView() and changed the MainView() content to this:
struct MainView: View {
#ObservedObject var model: MainViewModel
if let item = model.selectedItem {
SecondView(item: item)
}
}
Inside SecondView(), how can I access the item data so that I can use item.title inside SecondView() now?
In order to pass item to SecondView, declare item as a let property and then when you call it with SecondView(item: item), SecondView can refer to item.title.
Here is a complete example expanding on your code:
import SwiftUI
struct Item {
let title = "Test Title"
}
class MainViewModel: ObservableObject {
#Published var selectedItem: Item? = Item()
}
struct MainView: View {
#ObservedObject var model: MainViewModel
var body: some View {
if let item = model.selectedItem {
SecondView(item: item)
}
}
}
struct SecondView: View {
let item: Item
var body: some View {
Text(item.title)
}
}
struct ContentView: View {
#StateObject private var model = MainViewModel()
var body: some View {
MainView(model: model)
}
}
I am working on a SwiftUI view where I have it populates other subviews within the main view. My question is how can I call something in the main view from within a sub view?
Here is what the code looks like for my main view:
struct MovieList: View {
#ObservedObject var viewModel = MovieViewModel()
var body: some View {
VStack {
ScrollView(.vertical) {
VStack {
ForEach(self.viewModel.movie) { movie in
MovieView(movie: movie)
}
}
}
}
.navigationBarTitle("Movies")
.onAppear {
self.viewModel.fetchMovies() // Fetch all movies and cause entire view to refresh and populate movies
}
}
}
This main view populates a list of movies by adding multiple MovieView instances.
Here is some example code for the MovieView:
struct MovieView: View {
let movie: Movie
var body: some View {
VStack(alignment: .leading) {
HStack {
Text(“Movie Title: \(movie.title)”)
}.padding([.top, .leading, .bottom])
Button("Do not show this movie") {
// Update user prefers to hide the movie.
// But also somehow from within here call viewModel.fetchMovies() in the other view to refresh the movies list
}
}
}
}
So for example, from within one of the MovieView views, how can I have fetchMovies() from within the main view called so that everything gets updated?
Essentially a list of items is being populated and I would like for any one of these to have the ability to refresh/ perform some action on the entire main view
In terms of updating the Movie itself, as was pointed out in the comments, you probably want to pass a Binding to it. See the changes to the ForEach.
In terms of calling fetchMovies again, you can either pass the entire ObservableObject to the child view or just pass a reference to the function you need (which I've shown below):
struct Movie : Identifiable {
var id = UUID()
var title : String
var isHidden: Bool
}
class MovieViewModel : ObservableObject {
#Published var movies = [Movie]()
func fetchMovies() {
//fetch
}
}
struct MovieList: View {
#ObservedObject var viewModel = MovieViewModel()
var body: some View {
VStack {
ScrollView(.vertical) {
VStack {
ForEach($viewModel.movies) { $movie in
MovieView(movie: $movie, fetchMovies: viewModel.fetchMovies)
}
}
}
}
.navigationBarTitle("Movies")
.onAppear {
self.viewModel.fetchMovies()
}
}
}
struct MovieView: View {
#Binding var movie: Movie
var fetchMovies : () -> Void
var body: some View {
VStack(alignment: .leading) {
HStack {
Text("Movie Title: \(movie.title)")
}.padding([.top, .leading, .bottom])
Button("Do not show this movie") {
movie.isHidden = true
fetchMovies()
}
}
}
}
Sorry if my question is silly, I am a beginner to programming. I have a Navigation Link to a detail view from a List produced from my view model's array. In the detail view, I want to be able to mutate one of the tapped-on element's properties, but I can't seem to figure out how to do this. I don't think I explained that very well, so here is the code.
// model
struct Activity: Identifiable {
var id = UUID()
var name: String
var completeDescription: String
var completions: Int = 0
}
// view model
class ActivityViewModel: ObservableObject {
#Published var activities: [Activity] = []
}
// view
struct ActivityView: View {
#StateObject var viewModel = ActivityViewModel()
#State private var showingAddEditActivityView = false
var body: some View {
NavigationView {
VStack {
List {
ForEach(viewModel.activities, id: \.id) {
activity in
NavigationLink(destination: ActivityDetailView(activity: activity, viewModel: self.viewModel)) {
HStack {
VStack {
Text(activity.name)
Text(activity.miniDescription)
}
Text("\(activity.completions)")
}
}
}
}
}
.navigationBarItems(trailing: Button("Add new"){
self.showingAddEditActivityView.toggle()
})
.navigationTitle(Text("Activity List"))
}
.sheet(isPresented: $showingAddEditActivityView) {
AddEditActivityView(copyViewModel: self.viewModel)
}
}
}
// detail view
struct ActivityDetailView: View {
#State var activity: Activity
#ObservedObject var viewModel: ActivityViewModel
var body: some View {
VStack {
Text("Number of times completed: \(activity.completions)")
Button("Increment completion count"){
activity.completions += 1
updateCompletionCount()
}
Text("\(activity.completeDescription)")
}
}
func updateCompletionCount() {
var tempActivity = viewModel.activities.first{ activity in activity.id == self.activity.id
}!
tempActivity.completions += 1
}
}
// Add new activity view (doesn't have anything to do with question)
struct AddEditActivityView: View {
#ObservedObject var copyViewModel : ActivityViewModel
#State private var activityName: String = ""
#State private var description: String = ""
var body: some View {
VStack {
TextField("Enter an activity", text: $activityName)
TextField("Enter an activity description", text: $description)
Button("Save"){
// I want this to be outside of my view
saveActivity()
}
}
}
func saveActivity() {
copyViewModel.activities.append(Activity(name: self.activityName, completeDescription: self.description))
print(copyViewModel.activities)
}
}
In the detail view, I am trying to update the completion count of that specific activity, and have it update my view model. The method I tried above probably doesn't make sense and obviously doesn't work. I've just left it to show what I tried.
Thanks for any assistance or insight.
The problem is here:
struct ActivityDetailView: View {
#State var activity: Activity
...
This needs to be a #Binding in order for changes to be reflected back in the parent view. There's also no need to pass in the entire viewModel in - once you have the #Binding, you can get rid of it.
// detail view
struct ActivityDetailView: View {
#Binding var activity: Activity /// here!
var body: some View {
VStack {
Text("Number of times completed: \(activity.completions)")
Button("Increment completion count"){
activity.completions += 1
}
Text("\(activity.completeDescription)")
}
}
}
But how do you get the Binding? If you're using iOS 15, you can directly loop over $viewModel.activities:
/// here!
ForEach($viewModel.activities, id: \.id) { $activity in
NavigationLink(destination: ActivityDetailView(activity: $activity)) {
HStack {
VStack {
Text(activity.name)
Text(activity.miniDescription)
}
Text("\(activity.completions)")
}
}
}
And for iOS 14 or below, you'll need to loop over indices instead. But it works.
/// from https://stackoverflow.com/a/66944424/14351818
ForEach(Array(zip(viewModel.activities.indices, viewModel.activities)), id: \.1.id) { (index, activity) in
NavigationLink(destination: ActivityDetailView(activity: $viewModel.activities[index])) {
HStack {
VStack {
Text(activity.name)
Text(activity.miniDescription)
}
Text("\(activity.completions)")
}
}
}
You are changing and increment the value of tempActivity so it will not affect the main array or data source.
You can add one update function inside the view model and call from view.
The view model is responsible for this updation.
class ActivityViewModel: ObservableObject {
#Published var activities: [Activity] = []
func updateCompletionCount(for id: UUID) {
if let index = activities.firstIndex(where: {$0.id == id}) {
self.activities[index].completions += 1
}
}
}
struct ActivityDetailView: View {
var activity: Activity
var viewModel: ActivityViewModel
var body: some View {
VStack {
Text("Number of times completed: \(activity.completions)")
Button("Increment completion count"){
updateCompletionCount()
}
Text("\(activity.completeDescription)")
}
}
func updateCompletionCount() {
self.viewModel.updateCompletionCount(for: activity.id)
}
}
Not needed #State or #ObservedObject for details view if don't have further action.
I am building a complex interface in SwiftUI that I need to break into multiple extensions in order to be able to compile the code, but I can't figure out how to pass data between the extension and the body structure.
I made a simple code to explain it :
class Search: ObservableObject {
#Published var angle: Int = 10
}
struct ContentView: View {
#ObservedObject static var search = Search()
var body: some View {
VStack {
Text("\(ContentView.self.search.angle)")
aTest()
}
}
}
extension ContentView {
struct aTest: View {
var body: some View {
ZStack {
Button(action: { ContentView.search.angle = 11}) { Text("Button")}
}
}
}
}
When I press the button the text does not update, which is my issue. I really appreciate any help you can provide.
You can try the following:
struct ContentView: View {
#ObservedObject var search = Search()
var body: some View {
VStack {
Text("\(ContentView.self.search.angle)")
aTest // call as a computed property
}
}
}
extension ContentView {
var aTest: some View { // not a separate `struct` anymore
ZStack {
Button(action: { self.search.angle = 11 }) { Text("Button")}
}
}
}
I am trying to create a list using ForEach and NavigationLink of an array of data.
I believe my code (see the end of the post) is correct but my build fails due to
"Missing argument for parameter 'index' in call" and takes me to SceneDelegate.swift a place I haven't had to venture before.
// Create the SwiftUI view that provides the window contents.
let contentView = ContentView()
I can get the code to run if I amend to;
let contentView = ContentView(habits: HabitsList(), index: 1)
but then all my links hold the same data, which makes sense since I am naming the index position.
I have tried, index: self.index (which is what I am using in my NavigationLink) and get a different error message - Cannot convert value of type '(Any) -> Int' to expected argument type 'Int'
Below are snippets of my code for reference;
struct HabitItem: Identifiable, Codable {
let id = UUID()
let name: String
let description: String
let amount: Int
}
class HabitsList: ObservableObject {
#Published var items = [HabitItem]()
}
struct ContentView: View {
#ObservedObject var habits = HabitsList()
#State private var showingAddHabit = false
var index: Int
var body: some View {
NavigationView {
List {
ForEach(habits.items) { item in
NavigationLink(destination: HabitDetail(habits: self.habits, index: self.index)) {
HStack {
VStack(alignment: .leading) {
Text(item.name)
.font(.headline)
Text(item.description)
}
}
}
}
}
}
}
}
struct HabitDetail: View {
#Environment(\.presentationMode) var presentationMode
#ObservedObject var habits: HabitsList
var index: Int
var body: some View {
NavigationView {
Form {
Text(self.habits.items[index].name)
}
}
}
}
You probably don't need to pass the whole ObservedObject to the HabitDetail.
Passing just a HabitItem should be enough:
struct HabitDetail: View {
#Environment(\.presentationMode) var presentationMode
let item: HabitItem
var body: some View {
// remove `NavigationView` form the detail view
Form {
Text(item.name)
}
}
}
Then you can modify your ContentView:
struct ContentView: View {
#ObservedObject var habits = HabitsList()
#State private var showingAddHabit = false
var body: some View {
NavigationView {
List {
// for every item in habits create a `linkView`
ForEach(habits.items, id:\.id) { item in
self.linkView(item: item)
}
}
}
}
// extract to another function for clarity
func linkView(item: HabitItem) -> some View {
// pass just a `HabitItem` to the `HabitDetail`
NavigationLink(destination: HabitDetail(item: item)) {
HStack {
VStack(alignment: .leading) {
Text(item.name)
.font(.headline)
Text(item.description)
}
}
}
}
}