Advanced Networking with URLSession

Sep 15 2022 · Swift 5.6, iOS 15, Xcode 13.4.1

Part 1: Upload Data, Background Downloads & WebSockets

03. Upload Data

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Notes: 03. Upload Data

URLSession - Apple Developer

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So far you’ve download data via URLSession tasks and its asynchronous transfer methods. But what if you need to upload data to a server instead?

cd ~/desktop

vapor new UploadServer

cd UploadServer

vapor xcode -y

struct MusicItemRating: Content {
  let id: String
  let artistName: String
  let trackName: String
  let rating: Int
}

app.post("upload") { req -> HTTPResponseStatus in
  let item = try req.content.decode(MusicItemRating.self)
        
  print("ID: \(item.id)")
  print("Artist Name: \(item.artistName)")
  print("Track Name: \(item.trackName)")
  print("Rating: \(item.rating)")
        
  return .ok
}

import SwiftUI

class RatingUploader: ObservableObject {
  private let session: URLSession
  private let sessionConfiguration: URLSessionConfiguration
  
  init() {
    self.sessionConfiguration = URLSessionConfiguration.default
    self.session = URLSession(configuration: sessionConfiguration)
  }
  
  func submit(rating: Int, for musicItem: MusicItem) async throws {
    
  }
}

guard let uploadURL = URL(string: "http://localhost:8080/upload") else {
  throw RatingUploadError.failedToCreateUploadURL
}

enum RatingUploadError: Error {
  case failedToCreateUploadURL
}

guard let uploadData = json.data(using: .utf8) else {
  throw RatingUploadError.failedToCreateUploadData
}

case failedToCreateUploadData

var request = URLRequest(url: uploadURL)
request.httpMethod = "Post"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")

let json = """
{
  "id": \(musicItem.id),
  "artistName": \(musicItem.artistName),
  "trackName": \(musicItem.trackName),
  "rating": \(rating)
}
"""

case invalidResponse

let (_, response) = try await session.upload(for: request, from: uploadData)

guard let httpResponse = response as? HTTPURLResponse,
      httpResponse.statusCode == 200
else {
  throw RatingUploadError.invalidResponse
}

@ObservedObject private var uploader: RatingUploader = RatingUploader()

@MainActor @State private var showRatingSubmitFailedAlert: Bool = false

private func submitRatingTapped() async {
  do {
    try await uploader.submit(rating: ratingView.rating, for: musicItem)

    ratingSubmitted = true
  } catch {
    showRatingSubmitFailedAlert = true
  }
}

.alert("Failed to submit your rating", isPresented: $showRatingSubmitFailedAlert) {
  Button(role: .cancel, action: {
    showRatingSubmitFailedAlert = false
  }, label: {
    Text("Dismiss")
  })
}
.alert("Rating submitted successfully", isPresented: $ratingSubmitted) {
  Button(role: .cancel, action: {
    ratingSubmitted = false
  }, label: {
    Text("Dismiss")
  })
}

VStack(spacing: 16) {
  ratingView
    .disabled(ratingSubmitted)
            
  Button {
    Task {
      await submitRatingTapped()
    }
  } label: {
    Text("Submit")
  }
  .disabled(ratingSubmitted)
}

let json = “””
{
  “id”: \(musicItem.id),
  “artistName”: “\(musicItem.artistName)”,
  “trackName”: “\(musicItem.trackName)”,
  “rating”: \(rating)
}
“””