SwiftUI Refresh list on state Change issue

Question

I am facing an issue in refreshing a list based on a state change. So I have a state variable which is using to show/hide a sheet , and while showing the sheet some data will be updated and the updated data needs to be shown on the list .This is my expectation , but the issue is that the list is not updating based on state change.As per my understanding , the entire View will be re-rendered when any state variable update happens, if so could anyone please check the below code and let me know why the list is not updating after the self.showSheet.toggle() inside the ProcessDocument closure:

struct DetailView: View {
    @Binding var document: Doc
    @State private var showSheet: Bool = false
    var body: some View {
        List {
            Section(header: smallHeaderText("DETAILS")) {
                DocTypesPicker(fleetId: fleet?.fleetId ?? "", docTypeId: $document.doc_type)
            }
            
            Section(header: smallHeaderText("IMAGES")) {
                NavigationLink(destination: DetailImagesPage(document: document) ) {
                    HStack {
                        let docImage = self. document.documentData?.first?.img ?? UIImage().jpegData(compressionQuality: 1.0)
                        Image(uiImage: UIImage(data: docImage!) ?? UIImage())
                            .resizable()
                            .frame(width: 60, height: 60, alignment: .center)
                        VStack(alignment: .leading) {
                            Spacer()
                            Text(self.pageCountFor(document: self.document))
                            Spacer()
                        }.padding(.leading, 14)
                    }
                }.listRowBackground(Color.white)
            }
            
            Section {
                HStack {
                    Spacer()
                    Button("Redo") {
                        self.showSheet.toggle()
                    }
                    Spacer()
                }
            }
        }
        .listStyle(GroupedListStyle())
        .sheet(isPresented: $showSheet) {
            ProcessDocument { docs in
                guard let docs = docs, let currentDoc = document.documentData else { return }

                document.removeFromDocumentData(currentDoc as NSSet)
                docs.forEach { doc in
                    let dateCreated = document.date_created
                    doc.doc_id = dateCreated
                    document.addToDocumentData(doc)
                }

                self.showSheet.toggle()
            }
        }
    }
}

user_12299030 · Answer

As per my understanding , the entire View will be re-rendered when any state variable update happens

Not this is not that way, updated only parts of view's body (subviews) explicitly dependent on that state (ie. if state inside Text - only that one Text will be updated, even if you have 10 more other views in body).

In your case there is no other dependency on showSheet inside body except sheet itself, so nothing, including List, is updated.

If you want to refresh entire List explicitly on showSheet the possible solution could be as follows

List {
 // ... content here
}
.id(showSheet)    // << here !!

SwiftUI Refresh list on state Change issue

1 Answers