Toggle Sidebar in SwiftUI NavigationView on macOS

While you could try to perform #selector(NSSplitViewController.toggleSidebar(_:)) on keyWindow?.contentViewController or keyWindow?.firstResponder?, it appears that this doesn't work consistently in some situations.

Instead, you can use this command:

NSApp.sendAction(#selector(NSSplitViewController.toggleSidebar(_:)), to: nil, from: nil)

It sends the toggleSidebar selector to the first object that can react to it, meaning, the only sidebar in the current window. This behavior is better documented on Apple's documentation website.

---

This method is the default implementation used by the SidebarCommands() menu item. This is found by adding the Toggle Sidebar menu item, then fetching it's selector like so:

let menu = NSApp.mainMenu!.items.first(where: { $0.title == "View" })!
let submenu = menu.submenu!.items.first(where: { $0.title == "Toggle Sidebar" })!
submenu.target // nil
submenu.action // #selector(toggleSidebar:)

This means that it will most likely be more consistent (and supported) than the other methods.

Since macOS Big Sur beta 4 you can add default sidebar commands with SwiftUI 2.0.

var body: some Scene {
    WindowGroup {
        NavigationView {
            Group {
                SidebarView()
                ContentView()
            }
        }
    }
    .commands {
        SidebarCommands()
    }
}

This code will add the "Toggle Sidebar" shortcut:

SidebarView code:

var body: some View {
    List {
        ForEach(0..<5) { index in
            Text("\(index)")
        }
    }
    .listStyle(SidebarListStyle())
}

In SwiftUI 2.0 you can use NSApp.keyWindow?.firstResponder?.tryToPerform(#selector(NSSplitViewController.toggleSidebar(_:)), with: nil) with a toolbar button like this:

.toolbar {
    ToolbarItem(placement: .navigation) {
        #if os(macOS)
        Button(action: toggleSidebar, label: {
            Image(systemName: "sidebar.left")
        })
        #endif
    }
}

func toggleSidebar() {
    #if os(macOS)
    NSApp.keyWindow?.firstResponder?.tryToPerform(#selector(NSSplitViewController.toggleSidebar(_:)), with: nil)
    #endif
}