The Swift Reflection API and what you can do with it



Swift's reflection capabilities are based around a struct called Mirror. You create a mirror for a particular subject and the mirror will then let you query it.

Before we look at the API, let's define a simple data structure that we can experiment on.

import Foundation

public class Store {
    let storesToDisk: Bool = true
public class BookmarkStore: Store {
    let itemCount: Int = 10
public struct Bookmark {
   enum Group {
      case tech
      case news
   private let store = {
       return BookmarkStore()
   let title: String?
   let url: URL
   let keywords: [String]
   let group: Group

let aBookmark = Bookmark(title: "Appventure", url: URL(string: "")!, keywords: ["Swift", "iOS", "OSX"], group: .tech)

So, we have a Bookmark. Bookmarks can have titles, urls, keywords, and bookmarks can belong to a Group. There is also a BookmarkStore and a more general Store. So, how do we query this data structure at runtime?