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How to let users move rows in a list

Paul Hudson    @twostraws   

Updated for Xcode 12.0

SwiftUI gives us simple hooks into lists to let us move rows around by attaching an onMove(perform:) modifier to items in a list, and have it call a method of our choosing when a move operation happens. That method needs to accept a source IndexSet and a destination Int, like this:

func move(from source: IndexSet, to destination: Int) {

When moving several items it’s always a good idea to move the later ones first so that you avoid moving other items and getting your indexes confused. Fortunately, Swift’s sequences have a built-in way to move index sets for us, so we can just pass the parameters along and have it work correctly.

As an example, we could create a ContentView struct that sets up an array of three username strings, and asks SwiftUI to move them around calling a move() method. In order to activate moving – i.e., to make the drag handles appear – it also adds an edit button to the navigation view so the user can toggle editing mode.

Here’s the code:

struct ContentView: View {
    @State private var users = ["Paul", "Taylor", "Adele"]

    var body: some View {
        NavigationView {
            List {
                ForEach(users, id: \.self) { user in
                    Text(user)
                }
                .onMove(perform: move)
            }
            .navigationBarItems(trailing: EditButton())
        }
    }

    func move(from source: IndexSet, to destination: Int) {
        users.move(fromOffsets: source, toOffset: destination)
    }
}
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