SearchViewController 源码学习

SearchViewController.swift 源码：

class SearchViewController: UIViewController {
  @IBOutlet var searchBar: UISearchBar!
  @IBOutlet var tableView: UITableView!

  var searchResults = [SearchResult]()
  var hasSearched = false

  // 可借鉴 1： struct 声明常量
  struct TableView {
    struct CellIdentifiers {
      static let searchResultCell = "SearchResultCell"
      static let nothingFoundCell = "NothingFoundCell"
    }
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    tableView.contentInset = UIEdgeInsets(top: 50, left: 0, bottom: 0, right: 0)
    var cellNib = UINib(nibName: TableView.CellIdentifiers.searchResultCell, bundle: nil)
    tableView.register(cellNib, forCellReuseIdentifier: TableView.CellIdentifiers.searchResultCell)
    cellNib = UINib(nibName: TableView.CellIdentifiers.nothingFoundCell, bundle: nil)
    tableView.register(cellNib, forCellReuseIdentifier: TableView.CellIdentifiers.nothingFoundCell)
    searchBar.becomeFirstResponder()
  }

  // MARK: - Helper Methods
  func iTunesURL(searchText: String) -> URL {
    
    // 可借鉴 2：url 字符串 Encoding 处理，避免特殊字符出现问题
    let encodedText = searchText.addingPercentEncoding(withAllowedCharacters: CharacterSet.urlQueryAllowed)!
    let urlString = String(format: "https://itunes.apple.com/search?term=%@", encodedText)
    let url = URL(string: urlString)
    return url!
  }

  func performStoreRequest(with url: URL) -> Data? {
    do {
      return try Data(contentsOf: url)
    } catch {
      print("Download Error: \(error.localizedDescription)")
      showNetworkError()
      return nil
    }
  }

  func parse(data: Data) -> [SearchResult] {
    do {
      let decoder = JSONDecoder()
      let result = try decoder.decode(ResultArray.self, from: data)
      return result.results
    } catch {
      print("JSON Error: \(error)")
      return []
    }
  }

  func showNetworkError() {
    let alert = UIAlertController(title: "Whoops...", message: "There was an error accessing the iTunes Store. Please try again.", preferredStyle: .alert)

    let action = UIAlertAction(title: "OK", style: .default, handler: nil)
    alert.addAction(action)
    present(alert, animated: true, completion: nil)
  }
}

// MARK: - Search Bar Delegate
extension SearchViewController: UISearchBarDelegate {
  func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
    if !searchBar.text!.isEmpty {
      searchBar.resignFirstResponder()

      hasSearched = true
      searchResults = []

      let url = iTunesURL(searchText: searchBar.text!)
      print("URL: '\(url)'")

      // 可借鉴 3：数组排序
      if let data = performStoreRequest(with: url) {
        searchResults = parse(data: data)
        searchResults.sort { $0 < $1 }
      }

      tableView.reloadData()
    }
  }

  func position(for bar: UIBarPositioning) -> UIBarPosition {
    .topAttached
  }
}

// MARK: - Table View Delegate
extension SearchViewController: UITableViewDelegate, UITableViewDataSource {
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if !hasSearched {
      return 0
    } else if searchResults.count == 0 {
      return 1
    } else {
      return searchResults.count
    }
  }

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    if searchResults.count == 0 {
      return tableView.dequeueReusableCell(withIdentifier: TableView.CellIdentifiers.nothingFoundCell, for: indexPath)
    } else {
      let cell = tableView.dequeueReusableCell(withIdentifier: TableView.CellIdentifiers.searchResultCell, for: indexPath) as! SearchResultCell
      let searchResult = searchResults[indexPath.row]
      cell.nameLabel.text = searchResult.name
      if searchResult.artist.isEmpty {
        cell.artistNameLabel.text = "Unknown"
      } else {
        cell.artistNameLabel.text = String(format: "%@ (%@)", searchResult.artist, searchResult.type)
      }
      return cell
    }
  }

  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    tableView.deselectRow(at: indexPath, animated: true)
  }

  func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
    if searchResults.count == 0 {
      return nil
    } else {
      return indexPath
    }
  }
}

SearchResult 参数类：

class ResultArray: Codable {
  var resultCount = 0
  var results = [SearchResult]()
}

class SearchResult: Codable, CustomStringConvertible {
  var artistName: String? = ""
  var trackName: String? = ""
  var kind: String? = ""
  var trackPrice: Double? = 0.0
  var currency = ""
  var imageSmall = ""
  var imageLarge = ""
  var trackViewUrl: String?
  var collectionName: String?
  var collectionViewUrl: String?
  var collectionPrice: Double?
  var itemPrice: Double?
  var itemGenre: String?
  var bookGenre: [String]?

  enum CodingKeys: String, CodingKey {
    case imageSmall = "artworkUrl60"
    case imageLarge = "artworkUrl100"
    case itemGenre = "primaryGenreName"
    case bookGenre = "genres"
    case itemPrice = "price"
    case kind, artistName, currency
    case trackName, trackPrice, trackViewUrl
    case collectionName, collectionViewUrl, collectionPrice
  }

  var name: String {
    return trackName ?? collectionName ?? ""
  }

  var storeURL: String {
    return trackViewUrl ?? collectionViewUrl ?? ""
  }

  var price: Double {
    return trackPrice ?? collectionPrice ?? itemPrice ?? 0.0
  }

  var genre: String {
    if let genre = itemGenre {
      return genre
    } else if let genres = bookGenre {
      return genres.joined(separator: ", ")
    }
    return ""
  }

  var type: String {
    let kind = self.kind ?? "audiobook"
    switch kind {
    case "album": return "Album"
    case "audiobook": return "Audio Book"
    case "book": return "Book"
    case "ebook": return "E-Book"
    case "feature-movie": return "Movie"
    case "music-video": return "Music Video"
    case "podcast": return "Podcast"
    case "software": return "App"
    case "song": return "Song"
    case "tv-episode": return "TV Episode"
    default: break
    }
    return "Unknown"
  }

  var artist: String {
    return artistName ?? ""
  }

  var description: String {
    return "\nResult - Kind: \(kind ?? "None"), Name: \(name), Artist Name: \(artistName ?? "None")"
  }
}

func < (lhs: SearchResult, rhs: SearchResult) -> Bool {
  return lhs.name.localizedStandardCompare(rhs.name) == .orderedAscending
}

以后写代码，可借鉴的地方，见注释。