Change of selected row in Table for macOS-CodePudding

I use Table in my CoreData app for macOS

@FetchRequest(sortDescriptors: [NSSortDescriptor(key: "name", ascending: true)]) private var categories: FetchedResults<Categories>
@State private var selectedCategoryID: Categories.ID?

and I'm wondering how I could catch change of selected row. If I try .onChange() as shown below then code can't be compiled due to error "Cannot call value of non-function type 'Categories.ID?' (aka 'Optional<Optional>')"

Table(categories, selection: $selectedCategoryID) {
    TableColumn("Name", value \.name!)
    TableColumn("Type", value: \.type!)
}.onChange(of: selectedCategoryID {
    print("Selected row changed.")
}

Thank you.

CodePudding user response：

I finally found the root cause .onChange() must looks like

.onChange(of: selectedCategoryID) { selected in
    print("Selected row is \(selected)")
}

CodePudding user response：

onChange is "to trigger a side effect", e.g. something unrelated. If you want to update a related value, then a trick is to move it into a struct with some logic, e.g.

struct TableConfig {
    var selectedCategoryID: CategoryID? {
        didSet {
            counter  
        }
    }
    var counter = 0

    mutating func reset() {
        selectedCategoryID = nil
        counter = 0
    }
}
...
@State var config = TableConfig()
...
Table(categories, selection: $config.selectedCategoryID)