Chaining promises in Alamofire using Promisekit - swift

Question

I think this is a pretty common use case, but I couldn't find any best way to achieve it.
Some parts of my ios application require login. How do I achieve the following pattern using Alamofire and swift.
.request (.GET 'login_required_endpoint')
.responsejson(if statusCode == 401){
login()
continue with GETing
login_required_endpoint
What is the best way to achieve this.
Make a request
If server responds with 401(Unauthorized)
Ask user to login after saving all the request payload for previous request
After successful login, continue with request in [1] with payload saved
(I realize it is open-ended, but any help on how to make progress would be highly appreciated)

Answer 1

With the below, you can call handleRequest instead of Alamofire's request
import Alamofire
import PromiseKit
enum ServerError: ErrorType {
case Unauthorized
// add others as necessary
}
func handleRequest(method: Alamofire.Method, _ URLString: URLStringConvertible, parameters: [String: AnyObject]? = nil) -> Promise<AnyObject> {
return request(method, URLString, parameters: parameters).recover { error -> AnyObject in
switch error {
case ServerError.Unauthorized:
return login().then {
request(method, URLString, parameters: parameters)
}
default:
throw error
}
}
}
private func request(method: Alamofire.Method, _ URLString: URLStringConvertible, parameters: [String: AnyObject]? = nil) -> Promise<AnyObject> {
return Promise { fulfill, reject in
Alamofire.request(method, URLString, parameters: parameters).responseJSON { response in
switch response.result {
case .Success(let json):
fulfill(json)
case .Failure(let error):
if response.response?.statusCode == 401 {
reject(ServerError.Unauthorized)
}
else {
reject(error)
}
}
}
}
}
private func login() -> Promise<Void> {
// do what you need here...
return Promise()
}