SwiftUI passing an observed object into a new view and getting updates

Question

I am very new to swift working on my first app and having trouble having a view update. I am passing an object into a new view, however the new view does not update when there is change in the Firebase Database. Is there a way to get updates on the Gridview? I though by passing the observed object from the StyleboardView it would update the GridView however Gridview does not update. I am having trouble finding a way for the new Gridview to update and reload the images.

struct StyleBoardView: View {


@State private var showingSheet = false
@ObservedObject var model = ApiModel()
@State var styleboardname = ""

let userEmail = Auth.auth().currentUser?.email

var body: some View {
    NavigationView {
        VStack {
            Text("Select Style Board")
            List (model.list) {item in
                Button(item.styleboardname) {
                            showingSheet.toggle()
                        }
                        .sheet(isPresented: $showingSheet) {
                            GridView(item: item)
                        }
            }

struct GridView: View {
var item: Todo
@ObservedObject var model = ApiModel()
@State var newImage = ""
@State var loc = ""
@State var shouldShowImagePicker = false
@State var image: UIImage?

var body: some View {
    NavigationView {
        var posts = item.styleboardimages
        
       
        VStack(alignment: .leading){
            Text(item.styleboardname)
                    GeometryReader{ geo in
                        LazyVGrid(columns: [
                            GridItem(.flexible()),
                            GridItem(.flexible()),
                            GridItem(.flexible())
                        ], spacing: 3 ){
                            ForEach(posts.sorted(by: <), id: \.key) { key, value in
                                if #available(iOS 15.0, *) {
                                    AsyncImage(url: URL(string: value), transaction: Transaction(animation: .spring())) { phase in
                                        switch phase {
                                        case .empty:
                                            Color.purple.opacity(0.1)
                                     
                                        case .success(let image):
                                            image
                                                .resizable()
                                                .scaledToFill()
                                     
                                        case .failure(_):
                                            Image(systemName: "exclamationmark.icloud")
                                                .resizable()
                                                .scaledToFit()
                                     
                                        @unknown default:
                                            Image(systemName: "exclamationmark.icloud")
                                        }
                                    }
                                    .frame(width: 100, height: 100)
                                    .cornerRadius(20)

Use the `sheet(item:)` form instead of `sheet(isPresented:)` and pass your `item` as a parameter. See, for example: https://stackoverflow.com/questions/66286949/swift-ui-state-does-get-set-on-the-first-tap — jnpdx, Feb 13 '22 at 18:55

Yrb · Accepted Answer · 2022-02-13T19:05:50.287

You have a few problems with the code. First of all, the original view that creates the view model, or has created for it originally, should own the object. Therefore you declare it as a @StateObject.

struct StyleBoardView: View {
    
    @State private var showingSheet = false
    @StateObject var model = ApiModel() // @StateObject here
    @State var styleboardname = ""
    
    let userEmail = Auth.auth().currentUser?.email
    
    var body: some View {
        NavigationView {
            VStack {
                Text("Select Style Board")
                List ($model.list) { $item in // Change this to pass a Binding
                    Button(item.styleboardname) {
                        showingSheet.toggle()
                    }
                    .sheet(isPresented: $showingSheet) {
                        GridView(item: $item, model: model)
                    }
                }
            }
        }
    }
}

Since you are passing to a .sheet, that will not automatically be re-rendered when StyleBoardView's model changes, so you have to use a @Binding to cause GridView to re-render. Lastly, once you have your @StateObject, you pass that to your next view. Otherwise, you continually make new models, so updates to one will not update the other.

struct GridView: View {
    @Binding var item: Todo // Make this a @Binding so it reacts to the changes.
    @ObservedObject var model: ApiModel // Pass the originally created view model in.

    ...
    
    var body: some View {
        NavigationView {
            ...
        }
    }
}

Lastly, you did not post a Minimal, Reproducible Example (MRE). You also did not post the complete GridView struct. You may not even need your view model in that view as you do not use it in what you have posted.

score 0 · Answer 2 · answered Feb 13 '22 at 18:57

The problem is that you're initializing the model in an ObservedObject, and passing it down to another initialized Observed Object.

What you actually wanna do is use an @StateObject for where you initialize the model. And then use @ObservedObject with the type of the model you're passing down so that:

struct StyleBoardView: View {
@StateObject var model = ApiModel()

/** Code **/

struct GridView: View {
@ObservedObject var model: ApiModel

Notice the difference, an @ObservedObject should never initialize the model, it should only "inherit" (@ObservedObject var model: ApiModel) a model from a parent View, in this case, ApiModel.

SwiftUI passing an observed object into a new view and getting updates

2 Answers2