Three column NavigationView

A three column NavigationView is created using a similar approach as the two column NavigationView. The middle column has a fixed minimum width of 200 but the frame’s minWidth can be specified with a value greater than 200.

three column navigation

import SwiftUI

struct Group {
    let name: String
    let items: [String]
}

let groups = [
    Group(name: "Group A", items: ["Item 1", "Item 2"]),
    Group(name: "Group B", items: ["Item 3"]),
    Group(name: "Group C", items: ["Item 4", "Item 5", "Item 6"])
]

struct Sidebar: View {
    @State private var selection: String?

    var body: some View {
        List(groups, id: \.self.name) { group in
            NavigationLink(group.name, destination: Itembar(items: group.items), tag: group.name, selection: $selection)
        }
        .frame(minWidth: 150)
        .listStyle(SidebarListStyle())
        .toolbar {
            Button(
                action: {
                    NSApp.keyWindow?.contentViewController?.tryToPerform(#selector(NSSplitViewController.toggleSidebar(_:)), with: nil)
                }, label: {
                    Label("Toggle sidebar", systemImage: "sidebar.left")
            })
        }
    }
}

struct Itembar: View {
    let items: [String]
    @State private var selection: String?

    var body: some View {
        List(items, id: \.self) { item in
            NavigationLink(item, destination: DetailView(detailText: item), tag: item, selection: $selection)
        }
    }
}

struct DetailView: View {
    let detailText: String
    var body: some View {
        Text("The selection is \(detailText)")
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            Sidebar()
            Text("Select a Group")
            Text("Select an Item")
        }
        .frame(width: 700, height: 400)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Gavin Wiggins © 2021