遵循https://www.hackingwithswift.com/quick-start/swiftui/how-to-create-expanding-lists中的代码示例
struct Bookmark: Identifiable {
let id = UUID()
let name: String
let icon: String
var items: [Bookmark]?
// some example websites
static let apple = Bookmark(name: "Apple", icon: "1.circle")
static let bbc = Bookmark(name: "BBC", icon: "square.and.pencil")
static let swift = Bookmark(name: "Swift", icon: "bolt.fill")
static let twitter = Bookmark(name: "Twitter", icon: "mic")
// some example groups
static let example1 = Bookmark(name: "Favorites", icon: "star", items: [Bookmark.apple, Bookmark.bbc, Bookmark.swift, Bookmark.twitter])
static let example2 = Bookmark(name: "Recent", icon: "timer", …