SC #6：使用 async/await 的网络请求

Source: Dev.to

示例代码

func performPOSTURLRequest() async throws(NetworkingError) -> PostData {
  do {
    let request = try buildURLRequest()
    let (data, response) = try await URLSession.shared.data(for: request)

    guard let statusCode = (response as? HTTPURLResponse)?.statusCode else {
      throw NetworkingError.invalidStatusCode(statusCode: -1)
    }

    guard (200..<300).contains(statusCode) else {
      throw NetworkingError.invalidStatusCode(statusCode: statusCode)
    }

    let decodedResponse = try JSONDecoder().decode(PostResponse.self, from: data)
    print("The JSON response contains a name: \(decodedResponse.json.name) and an age: \(decodedResponse.json.age)")

    return decodedResponse.json

  } catch let error as EncodingError {
    throw .encodingFailed(innerError: error)
  } catch let error as DecodingError {
    throw .decodingFailed(innerError: error)
  } catch let error as URLError {
    throw .requestFailed(innerError: error)
  } catch let error as NetworkingError {
    throw error
  } catch {
    throw .otherError(innerError: error)
  }
}

注意事项

• 编译器会提示如果没有返回任何值，这在基于 closures 的实现中是不可能的。
• 虽然代码的某些部分会抛出 NetworkingError 类型的错误，但必须显式捕获它们；否则会被通用的 catch 捕获。
• URLSession.shared.data(for:) 在请求成功时返回 非可选 值；如果出现错误，则会抛出异常。