async/awaitによるURLSession data(from:)

最新のURLSession API

let (data, response) = try await URLSession.shared.data(from: URL(string: "https://api.example.com/items")!)

完全なフェッチ関数

func fetchItems() async throws -> [Item] {
  let url = URL(string: "https://api.example.com/items")!
  let (data, _) = try await URLSession.shared.data(from: url)
  return try JSONDecoder().decode([Item].self, from: data)
}

SwiftUIからの呼び出し

struct ItemList: View {
  @State private var items: [Item] = []
  var body: some View {
    List(items, id: \.id) { Text($0.name) }
      .task { items = (try? await fetchItems()) ?? [] }
  }
}

カスタムヘッダー用のURLRequest

var request = URLRequest(url: URL(string: "https://api.example.com/login")!)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = try? JSONEncoder().encode(LoginBody(email: "a@b.com", password: "pass"))
let (data, _) = try await URLSession.shared.data(for: request)

HTTPステータスの確認

let (data, response) = try await URLSession.shared.data(from: url)
guard let http = response as? HTTPURLResponse, http.statusCode == 200 else {
  throw URLError(.badServerResponse)
}
let item = try JSONDecoder().decode(Item.self, from: data)

キャンセル

let task = Task {
  let items = try await fetchItems()
  // ...
}
task.cancel() // cancels URLSession request if in-flight

データのアップロード

var request = URLRequest(url: uploadURL)
request.httpMethod = "POST"
let (data, _) = try await URLSession.shared.upload(for: request, from: imageData)

ファイルのダウンロード

let (fileURL, _) = try await URLSession.shared.download(from: remoteURL)
let destURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].appendingPathComponent("file.pdf")
try FileManager.default.moveItem(at: fileURL, to: destURL)

カスタムURLSession構成

let config = URLSessionConfiguration.default
config.timeoutIntervalForRequest = 30
config.requestCachePolicy = .reloadIgnoringLocalCacheData
let session = URLSession(configuration: config)

ストリーミング用のasync bytes

let (stream, _) = try await URLSession.shared.bytes(from: url)
for try await line in stream.lines {
  print(line)
}

URLProtocolによるテスト

class MockURLProtocol: URLProtocol {
  static var requestHandler: ((URLRequest) throws -> (HTTPURLResponse, Data))?
  // override canInit, startLoading, stopLoading
}

確認問題

レッスンのまとめ