I have a Classification class

@Model
final class Classification: Identifiable, Equatable {
    var id: UUID
    var image: String
    var background: Int
    var name: String
    var hasDeleted: Bool
    var notShow: Bool

    init(id: UUID = UUID(), image: String, background: Int, name: String, hasDeleted: Bool = false,notShow: Bool = false ) {
        self.id = id
        self.image = image
        self.background = background
        self.name = name
        self.hasDeleted = hasDeleted
        self.notShow = notShow
    }

    static let mockData = Classification(image: "questionmark", background: 0xFF0000, name: "请选择标签", hasDeleted: false)
}

And I have a TodoItem class which hava a attribute type Classification

@Model
final class TodoItem: Identifiable {
    var id: UUID
    var title: String
    var startTime: Date
    var endTime: Date
    var isCompleted: Bool
    var isLog: Bool
    var classification: Classification?

    init(id: UUID = UUID(),  title: String, startTime: Date, endTime: Date, isCompleted: Bool, isLog: Bool, classification: Classification?) {
        self.id = id
        self.title = title
        self.startTime = startTime
        self.endTime = endTime
        self.isCompleted = isCompleted
        self.isLog = isLog
        self.classification = classification
    }

    // 创建 Log
    convenience init(title: String, startTime: Date, endTime: Date, classification: Classification?) {
        self.init(id: UUID(), title: title, startTime: startTime, endTime: endTime, isCompleted: true, isLog: true, classification: classification)
    }

    static let mockDataTodo = TodoItem( title: "todo测试", startTime: Date(), endTime: Date(timeIntervalSinceNow: 3000), isCompleted: false, isLog: false, classification: nil)
    static let mockDataLog = TodoItem(title: "log测试", startTime: Date(timeIntervalSinceNow: -3000), endTime: Date(), classification: nil)
}

now A View show TodoItem data, B View show Classification data , A and B View in TabView. When I update Classification data in B View , A View will not update automatically and you must re-open the app before it will update.

// B View update data
@Environment(\.dismiss) var dismiss
    @Bindable var editTagInfo: Classification
    var modelContext: ModelContext
    let presetColors: [Int] = [0xFF0000, 0x00FF00, 0x0000FF]
    @State private var isSFPresented = false
    @State private var showDeleteAlert = false
    init(classificationId: PersistentIdentifier, in container: ModelContainer) {
        modelContext = ModelContext(container)
        modelContext.autosaveEnabled = false
        editTagInfo = modelContext.model(for: classificationId) as? Classification ?? Classification.mockData
    }

HStack {
                    ColorPicker("tag color", selection: colorValueBinding, supportsOpacity: false)
                        .padding(.trailing)
                    }

CircleButton(imageString: "checkmark", width: 35, backgroundColor: .green, imageColor: .white, ifGradient: true)
                        .onTapGesture {
                            withAnimation {
                                try! modelContext.save()
                                dismiss()
                            }
                        }

But how do you fetch your data in View A? If you add something in View B, you have to use either @Query which will automatically fetch new data from context, or run fetch to get the data from context.

Also try to add explicit relationship to class Classification

@Relationship(reverse: \TodoItem.classification) var todoItems: [TodoItem] = []

in init you can default it to emtpy array

in todoItems I used @Query to get data, and I added @Relationship , but still the existed todoItems won't change automatically ... And if I reopen app , the existed todoItem will change And after I changed classification , I create a new todoItem, It will follow my change too