Networking (URLSession)

Networking (URLSession)

Fetch and send JSON over HTTPS using URLSession with async/await, and integrate responses into SwiftUI.

GET Request with async/await

Use URLSession.shared.data(from:) with async/await to fetch data.

Syntax:

• let (data, response) = try await URLSession.shared.data(from: url)
• decode with JSONDecoder().decode

import SwiftUI
import Foundation

struct Todo: Decodable, Identifiable { let id: Int; let title: String }

func fetchTodos() async throws -> [Todo] {
  let url = URL(string: "https://jsonplaceholder.typicode.com/todos?_limit=2")!
  let (data, _) = try await URLSession.shared.data(from: url)
  return try JSONDecoder().decode([Todo].self, from: data)
}

struct NetworkingGetDemo: View {
  @State private var todos: [Todo] = []
  var body: some View {
    List(todos) { t in Text(t.title) }
      .task {
        do { todos = try await fetchTodos() } catch { print(error) }
      }
  }
}

import SwiftUI

struct ContentView: View {
  var body: some View { NetworkingGetDemo() }
}

import SwiftUI

@main
struct MyApp: App {
  var body: some Scene {
    WindowGroup { ContentView() }
  }
}

This example fetches a small JSON list with URLSession using async/await and displays it in a SwiftUI List.

Sample App: Notes (Networking)

Use @MainActor class VM: ObservableObject { @Published var items: [T] = []; func loadFromAPI() async { ... } } to separate concerns and load data in the background.

Syntax:

• @MainActor class VM: ObservableObject { @Published var items: [T] = []; func loadFromAPI() async { ... } }
• View: .task { await vm.loadFromAPI() } to kick off the async load
• API: let (data, _) = try await URLSession.shared.data(from: url), JSONDecoder().decode

import SwiftUI
import Foundation

struct NoteDTO: Decodable, Identifiable { let id: Int; let title: String; let body: String }

enum API {
  static func fetchNotes() async throws -> [NoteDTO] {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts?_limit=3")!
    let (data, _) = try await URLSession.shared.data(from: url)
    return try JSONDecoder().decode([NoteDTO].self, from: data)
  }
}

@MainActor
final class NotesViewModel: ObservableObject {
  @Published var notes: [NoteDTO] = []
  func loadFromAPI() async {
    do { notes = try await API.fetchNotes() }
    catch { print(error) }
  }
}

struct NotesView: View {
  @StateObject private var vm = NotesViewModel()
  var body: some View {
    List(vm.notes) { n in Text(n.title) }
      .task { await vm.loadFromAPI() }
  }
}

import SwiftUI

struct ContentView: View {
  var body: some View { NotesView() }
}

import SwiftUI

@main
struct MyApp: App {
  var body: some Scene {
    WindowGroup { ContentView() }
  }
}

This example separates concerns with an API helper and a ViewModel, then loads notes into a SwiftUI List on task.

POST JSON

Send JSON by encoding your payload and setting the request method and headers.

Syntax:

• var req = URLRequest(url:)
• req.httpMethod = "POST"
• req.setValue("application/json", forHTTPHeaderField: "Content-Type")
• req.httpBody = try JSONEncoder().encode(payload)
• let (_, resp) = try await URLSession.shared.data(for: req)

import SwiftUI
import Foundation

struct NewTodo: Encodable { let title: String; let completed: Bool }

func createTodo(_ todo: NewTodo) async throws -> Int {
  let url = URL(string: "https://jsonplaceholder.typicode.com/todos")!
  var req = URLRequest(url: url)
  req.httpMethod = "POST"
  req.setValue("application/json", forHTTPHeaderField: "Content-Type")
  req.httpBody = try JSONEncoder().encode(todo)
  let (_, resp) = try await URLSession.shared.data(for: req)
  return (resp as? HTTPURLResponse)?.statusCode ?? 0
}

struct NetworkingPostDemo: View {
  @State private var status: Int? = nil
  var body: some View {
    VStack(spacing: 12) {
      Button("Create Todo") {
        Task {
          do { status = try await createTodo(NewTodo(title: "Demo", completed: false)) }
          catch { print(error); status = nil }
        }
      }
      if let status { Text("Status: \(status)") }
    }
    .padding()
  }
}

import SwiftUI

struct ContentView: View {
  var body: some View { NetworkingPostDemo() }
}

import SwiftUI

@main
struct MyApp: App {
  var body: some Scene {
    WindowGroup { ContentView() }
  }
}

This example sends a JSON payload with a POST request and returns the HTTP status code from the response.