How to retry request with Alamofire?

Question

Is there a way, in Alamofire, to re-send the request if the response code from the first request is 401, where I can refresh the token and retry my request again?

The problem is that I'm using MVVM and also completion handler already. In my ViewModel the request function looks like:

public func getProfile(completion: @escaping (User?) -> Void) {
    guard let token = UserDefaults.standard.value(forKey: Constants.shared.tokenKey) else { return }

    let headers = ["Authorization": "Bearer \(token)"]

    URLCache.shared.removeAllCachedResponses()
    Alamofire.request(Constants.shared.getProfile, method: .get, parameters: nil, encoding: URLEncoding.default, headers: headers).responseJSON { (response) in
        switch response.result {
        case .success:
            guard let data = response.data else { return }

            if JSON(data)["code"].intValue == 401 {
                // here I need to refresh my token and re-send the request
            } else {
                let user = User(json: JSON(data)["data"])
                completion(user)
            }

            completion(nil)
        case .failure(let error):
            print("Failure, ", error.localizedDescription)
            completion(nil)
        }
    }
}

and from my ViewController I call it like:

viewModel.getProfile { (user) in
    if let user = user {
        ...
    }
}

So I do not know how can retry my request without using a new function, so I can still get my user response from completion part in my ViewController. Maybe someone can show me the right path. Thanks in advance!

Answer 1

To retry a request create a Request wrapper and use the RequestInterceptor protocol of Alamofire like this

final class RequestInterceptorWrapper: RequestInterceptor {

// Retry your request by providing the retryLimit. Used to break the flow if we get repeated 401 error
var retryLimit = 0

func retry(_ request: Request, for session: Session, dueTo error: Error, completion: @escaping (RetryResult) -> Void) {

    guard let statusCode = request.response?.statusCode else { return }
    switch statusCode {
    case 200...299:
        completion(.doNotRetry)
    default:
        if request.retryCount < retryLimit {
            completion(.retry)
            return
        }
        completion(.doNotRetry)
    }
}

//This method is called on every API call, check if a request has to be modified optionally

func adapt(_ urlRequest: URLRequest, for session: Session, completion: @escaping (Result<URLRequest, Error>) -> Void) {
    //Add any extra headers here 
    //urlRequest.addValue(value: "", forHTTPHeaderField: "")
    completion(.success(urlRequest)) 
   }
}

Usage: For every API request, the adapt() method is called, and on validate() the retry method is used to validate the status code. retryLimit can be set by creating an instance of the interceptor here Providing the retryLimit would call the API twice if the response was an error

let interceptor = RequestInterceptorWrapper() 
func getDataFromAnyApi(completion: @escaping (User?) -> Void)) {
    interceptor.retryLimit = 2
    AF.request(router).validate().responseJSON { (response) in
          
         guard let data = response.data else { 
            completion(nil)
            return 
         }
         // convert to User and return
         completion(User)
    }
}