Get final URL by following redirection using Swift • Jonathan Dionne

Swift’s URLResolver class simplifies handling URL redirects using async-await. It performs a lightweight “HEAD” request to only fetch headers, efficiently detecting if a URL redirects to another location. If there’s a redirect, it returns the new URL; otherwise, it returns the original. This approach utilizes Swift’s modern concurrency features for straightforward and efficient URL management in apps.

Snippet

import Foundation

class URLResolver {
    func resolve(url: URL) async -> URL? {
        await withCheckedContinuation { continuation in
            var request = URLRequest(url: url)
            request.httpMethod = "HEAD"

            let task = URLSession.shared.dataTask(with: request) { _, response, error in
                guard let httpResponse = response as? HTTPURLResponse, error == nil else {
                    continuation.resume(returning: nil)
                    return
                }

                if let location = httpResponse.value(forHTTPHeaderField: "Location"),
                   let redirectedURL = URL(string: location) {
                    continuation.resume(returning: redirectedURL)
                } else {
                    continuation.resume(returning: httpResponse.url)
                }
            }
            task.resume()
        }
    }
}

Usage

Here’s a simple example demonstrating how to use URLResolver in a Swift application:

// Use the URLResolver
func fetchFinalURL(from urlString: String) async {
    guard let url = URL(string: urlString) else {
        print("Invalid URL")
        return
    }

    let resolver = URLResolver()
    if let finalURL = await resolver.resolve(url: url) {
        print("Final URL is: \(finalURL)")
    } else {
        print("Failed to resolve URL or no redirection found.")
    }
}

// Example usage
Task {
    await fetchFinalURL(from: "http://example.com")
}