How to handle URL redirects in SwiftUI? - url

Question

I have the following code that fills an Image with the favicon of a website:
import SwiftUI
struct ContentView: View {
#State var website = "https://www.stackoverflow.com/favicon.ico"
#State var favicon : String?
var body: some View {
VStack {
if favicon != nil {
Image(uiImage: favicon!.toImage()!)
}
TextField("Sito", text: $website).padding()
Button(action: {
website = "https://www." + website + ".com/favicon.ico"
}, label: {
Text("Complete URL")
}).padding()
Button(action: {
if let url = URL(string: website) {
let session = URLSession.shared.dataTask(with: url) { [self] (data,response,error) in
if let error = error {
debugPrint(error.localizedDescription)
return
}
if let data = data {
var immagineTemp : UIImage = UIImage(systemName: "questionmark")!
if UIImage(data: data) != nil {
immagineTemp = UIImage(data: data)!
} else {
debugPrint("URL was redirected")
}
favicon = immagineTemp.toString()
}
}
session.resume()
}
}, label: {
Text("Get favicon")
}).padding()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
extension String {
func toImage() -> UIImage? {
if let data = Data(base64Encoded: self, options: .ignoreUnknownCharacters){
return UIImage(data: data)
}
return nil
}
}
extension UIImage {
func toString() -> String? {
let data: Data? = self.pngData()
return data?.base64EncodedString(options: .endLineWithLineFeed)
}
}
Usually, the var website is empty and can be filled throught the TextField, but for the purpose of this example I filled it with that URL, because if you use the Stackoverflow website to download the favicon, as I wrote in the code above, it doesn't work because the URL "https://www.stackoverflow.com/favicon.ico" redirects you to "https://cdn.sstatic.net/Sites/stackoverflow/Img/favicon.ico?v=ec617d715196", which is where the Stackoverflow favicon is. Because of this, "immagineTemp = UIImage(data: data)!" results nil, and it goes in the brackets where there's the debugPrint("URL was redirected").
What I would like it to do, is to automatically detect the fact that a URL redirects you to another one, so that it can continue on its own to download the favicon. Is there a way to do it?

Answer 1

At first I thought you could cast the response (which is of type URLResponse) as an HTTPURLResponse, then check the property statusCode of that object.
But on further inspection, it seems like the way to go is to implement NSURLSessionTaskDelegate, and more specifically the following method:
optional func urlSession(_ session: URLSession,
task: URLSessionTask,
willPerformHTTPRedirection response: HTTPURLResponse,
newRequest request: URLRequest,
completionHandler: #escaping (URLRequest?) -> Void)
See the Apple documentation here: https://developer.apple.com/documentation/foundation/urlsessiontaskdelegate/1411626-urlsession