Prevent redirect response with Alamofire in Swift

Question

I'm looking for example code how to prevent redirect response (status code 3xx) when request web api. I'm using Swift with Alamofire 1.2. I have tried:

delegate.taskWillPerformHTTPRedirection = { (session: NSURLSession!, task: NSURLSessionTask!, response: NSHTTPURLResponse!, request: NSURLRequest!) in
            return nil
        }

but not work

I've also tried: https://github.com/Alamofire/Alamofire/pull/350/files and have changed my own code to:

    var acc = self.txtAccount.text
    var pwd = self.txtPassword.text
    var url : String = "http://10.1.0.2:8081/wordpress/wp-json/users/me"
    let delegate = Alamofire.Manager.sharedInstance.delegate
    delegate.taskWillPerformHTTPRedirection = { (session: NSURLSession!, task: NSURLSessionTask!, response: NSHTTPURLResponse!, request: NSURLRequest!) in

        var request = NSMutableURLRequest(URL: NSURL(string: url)!)
        request.HTTPMethod = "GET"

        var credential = "\(acc):\(pwd)"
        var authData = credential.dataUsingEncoding(NSUTF8StringEncoding)
        var encodedAuthData = authData?.base64EncodedStringWithOptions(nil)
        var authValue = "Basic \(encodedAuthData!)"

        request.setValue(authValue, forHTTPHeaderField: "Authorization")
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.setValue("application/json", forHTTPHeaderField: "Accept")
        return request
    }

    //I've implemented URLRequestConvertible 'Router'. it also have call the same above url
    Alamofire.request(Router.Authorize(acc, pwd))
        .response({(request, response, data, error) in
            println(request)
        })

But it's not worked and seem like turned to infinite loop. I tested on Charles.

Answer 1

Alternative (code snippet) solution using AlamoFire 2.4 (Xcode7). In my case, I always expect a redirect. (I am unpacking a shortened link.) If the completion in the request.response call runs, that is an error to me.

func printRedirectUrl() {

    // taskWillPerformHTTPRedirectionWithCompletion: ((NSURLSession, NSURLSessionTask, NSHTTPURLResponse, NSURLRequest, NSURLRequest? -> Void) -> Void)?
    Alamofire.Manager.sharedInstance.delegate.taskWillPerformHTTPRedirectionWithCompletion = { session, task, response, request, completion in
        // request.URL has the redirected URL inside of it, no need to parse the body
        print("REDIRECT Request: \(request)")
        if let url = request.URL {
            print("Extracted URL: \(url)")
        }
        Alamofire.Manager.sharedInstance.delegate.taskWillPerformHTTPRedirection = nil // Restore redirect abilities
        return
    }

    // We expect a redirect, so the completion of this call should never execute
    let url = NSURL(string: "https://google.com")
    let request = Alamofire.request(.GET, url!)
    request.response { request, response, data, error in
        print("Logic Error, response should NOT have been called for request: \(request)")
        Alamofire.Manager.sharedInstance.delegate.taskWillPerformHTTPRedirection = nil // Restore redirect abilities - just in case
    }
}

REDIRECT Request: { URL: https://www.google.com/ }

Extracted URL: https://www.google.com/

Answer 2

It looks like returning nil can possibly cause a deadlock. Instead, try to create a new NSURLRequest with the same original URL. See @jhersh's notes in a previous Alamofire PR along with the comments and implementation in his tests.

How to Stop a Redirect

func disallowRedirect() {
    let URL = "http://google.com/"
    let delegate = Alamofire.Manager.sharedInstance.delegate

    delegate.taskWillPerformHTTPRedirection = { session, task, response, request in
        return NSURLRequest(URL: NSURL(string: URL)!)
    }

    let request = Alamofire.request(.GET, URL)
    request.response { request, response, data, error in
        println("Request: \(request)")
        println("Response: \(response)")
        println("Data: \(NSString(data: data as! NSData, encoding: NSUTF8StringEncoding))")
        println("Error: \(error)")
    }
}

disallowRedirect()

The fact that you cannot pass nil into the NSURLSessionTaskDelegate method's completionHandler looks like a bug. I'm going to file a radar for this and I'll post a link to the bug report once I'm finished.

Answer 3

In Swift 4,

let delegate = Alamofire.SessionManager.default.delegate

        delegate.taskWillPerformHTTPRedirection = { (session, task, response, request) -> URLRequest? in
           // print("REDIRECT Request: \(request)")
            return nil
        }

Answer 4

I don't know if your version of Alamofire has a support for public delegate. Last time I checked delegate was private. I am using the changes made by @jhersh. You can check his additions and how to use delegate by followin github pr. https://github.com/Alamofire/Alamofire/issues/314