URL / URLComponents / URLSession

import Foundation

// Create a URL
let url = URL(string: "https://example.com/api/users")!
print("URL: \(url)")
print("Host: \(url.host ?? "none")")
print("Path: \(url.path)")

// Build a URL with URLComponents
var components = URLComponents()
components.scheme = "https"
components.host = "api.example.com"
components.path = "/search"
components.queryItems = [
    URLQueryItem(name: "q", value: "Swift"),
    URLQueryItem(name: "page", value: "1")
]

if let builtURL = components.url {
    print("Built URL: \(builtURL)")
}

// GET request with URLSession
struct Post: Codable {
    let id: Int
    let title: String
}

func fetchPost(id: Int) async throws -> Post {
    let url = URL(string: "https://jsonplaceholder.typicode.com/posts/\(id)")!
    let (data, response) = try await URLSession.shared.data(from: url)

    guard let httpResponse = response as? HTTPURLResponse,
          httpResponse.statusCode == 200 else {
        throw URLError(.badServerResponse)
    }

    return try JSONDecoder().decode(Post.self, from: data)
}

Task {
    do {
        let post = try await fetchPost(id: 1)
        print("Title: \(post.title)")
    } catch {
        print("Error: \(error)")
    }
}

// POST request with URLSession
func postData(to url: URL, body: Data) async throws -> Data {
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    request.httpBody = body

    let (data, _) = try await URLSession.shared.data(for: request)
    return data
}

URL: https://example.com/api/users
Host: example.com
Path: /api/users
Built URL: https://api.example.com/search?q=Swift&page=1
Title: sunt aut facere repellat provident occaecati excepturi optio reprehenderit

Swift Concurrency's URLSession.shared.data(from:) fetches data asynchronously and suspends execution with await until it completes. This is far simpler than the traditional callback-based approach.

When a URL contains special characters (spaces, non-ASCII characters, etc.), use URLComponents to handle percent-encoding automatically. URLSession does not block the main thread by default. However, any UI updates must be performed on the @MainActor or via DispatchQueue.main.

For JSON decoding, see Codable / Encodable / Decodable.