Added iOS example for add-to-app Pigeon (#722)

add_to_app/books/ios_books/IosBooks/ViewController.swift

@@ -0,0 +1,131 @@
+// Copyright 2020 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import Flutter
+import UIKit
+
+class ViewController: UITableViewController, BKHostBookApi {
+  private var books: [BKBook] = []
+  private var api: BKFlutterBookApi!
+  private var editingIndex: Int = -1
+
+  override func viewDidLoad() {
+    super.viewDidLoad()
+    self.navigationItem.title = "Books"
+    let appDelegate = UIApplication.shared.delegate as! AppDelegate
+    BKHostBookApiSetup(appDelegate.engine.binaryMessenger, self)
+    api = BKFlutterBookApi.init(binaryMessenger: appDelegate.engine.binaryMessenger)
+    if let url = URL(
+      string: "https://www.googleapis.com/books/v1/volumes?q=greenwood+tulsa&maxResults=15")
+    {
+      self.loadBooks(url: url) { (newBooks) in
+        if let newBooks = newBooks {
+          self.books = newBooks
+          self.tableView.reloadData()
+        }
+      }
+    }
+  }
+
+  /**
+   Loads a JSON file from the supplied URL, parses it and calls the callback with the array of
+   parsed books on the main thread.
+   */
+  func loadBooks(url: URL, completion: @escaping ([BKBook]?) -> Void) {
+    URLSession.shared.dataTask(with: url) { data, response, error in
+      if let data = data {
+        do {
+          if let json = try JSONSerialization.jsonObject(with: data, options: [])
+            as? [String: Any]
+          {
+            var newBooks: [BKBook] = []
+            for item in json["items"] as! [[String: Any]] {
+              let volumeInfo = item["volumeInfo"] as! [String: Any]
+              let title = volumeInfo["title"] as! String
+              let subtitle = volumeInfo["subtitle"] as! String?
+              let authors = (volumeInfo["authors"] as! [String]).joined(separator: " & ")
+              let pageCount = volumeInfo["pageCount"] as! Int32
+              let publishedDate = volumeInfo["publishedDate"] as! String
+              let summary = volumeInfo["description"] as! String
+              let book: BKBook = BKBook.init()
+              book.author = authors
+              book.title = title
+              book.subtitle = subtitle
+              book.title = title
+              book.pageCount = NSNumber.init(value: pageCount)
+              book.publishDate = publishedDate
+              book.summary = summary
+              newBooks.append(book)
+            }
+            DispatchQueue.main.async {
+              completion(newBooks)
+            }
+          }
+        } catch let error {
+          print("json decode error: \(error)")
+          completion(nil)
+        }
+      }
+    }.resume()
+  }
+
+  override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+    return self.books.count
+  }
+
+  override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath)
+    -> UITableViewCell
+  {
+    let cell: BookCell = self.tableView.dequeueReusableCell(withIdentifier: "BookCell") as! BookCell
+    let bookInfo = books[indexPath.row]
+    cell.title.text = bookInfo.title
+    cell.subtitle.text = bookInfo.subtitle
+    if let author = bookInfo.author {
+      cell.byLine.text = "by: \(author)"
+    }
+    weak var weakSelf = self
+    let editAction = UIAction(title: "Edit") { (action) in
+      if let weakSelf = weakSelf {
+        weakSelf.editItem(index: indexPath.row)
+      }
+    }
+    cell.editButton.removeTarget(nil, action: nil, for: .allEvents)
+    cell.editButton.addAction(editAction, for: UIControl.Event.touchUpInside)
+    return cell
+  }
+
+  /**
+   Presents the FlutterViewController that edits the book at the supplied index.
+   */
+  func editItem(index: Int) {
+    let appDelegate = UIApplication.shared.delegate as! AppDelegate
+    let flutterViewController = FlutterViewController.init(
+      engine: appDelegate.engine, nibName: nil, bundle: nil)
+    self.editingIndex = index
+    api.displayBookDetails(self.books[index]) { (error) in
+      if let error = error {
+        print(error)
+      }
+    }
+    self.present(flutterViewController, animated: true, completion: nil)
+  }
+
+  /**
+   Called by Pigeon when the FlutterViewController is dismissed without accepting any edits.
+   */
+  func cancel(_ error: AutoreleasingUnsafeMutablePointer<FlutterError?>) {
+    self.editingIndex = -1
+    self.dismiss(animated: true, completion: nil)
+  }
+
+  /**
+   Called by Pigeon when edits to the book are accepted in the FlutterViewController.
+   */
+  func finishEditing(_ input: BKBook, error: AutoreleasingUnsafeMutablePointer<FlutterError?>) {
+    self.books[editingIndex] = input
+    self.tableView.reloadData()
+    self.editingIndex = -1
+    self.dismiss(animated: true, completion: nil)
+  }
+}