iOS rxSwift: retryWhen updating refresh token - ios

Question

I have a static function calling a network service.
When the 400 response code happens I would like to redo the network call.
The current code is working, except that the refreshToken in the header does not update between one try and another.
I think that the problem is because the Observable created but the request function does not update at the retry.
I rode on the web that I should use a deferred method on the Observable, but I don't know how.
I've tried moving the code: headers = [HeaderKeys.refreshToken.rawValue: "test test"] anywhere but still it never makes a call with the "test test" refresh token. it always uses the old one.
How can I fix this?
static func getAccessToken() -> Observable<GetAccessTokenResponse> {
var retryCounter = 0
let maxRetryCounter = 3
let delayRetry = 10.0
guard let refreshToken = NetworkHelper.shared.refreshToken else {
return Observable.error(AuthenticationError.networkError)
}
var headers = [HeaderKeys.refreshToken.rawValue: refreshToken]
return NetworkHelper.shared
.request(url: CoreAPI.accessToken.url, request: nil, headers: headers, responseType: GetAccessTokenResponse.self, method: .get, encoding: nil)
.catchError({ (error) -> Observable<(GetAccessTokenResponse?, Int)> in
return Observable.error(AuthenticationError.networkError)
})
.flatMap({ (response) -> Observable<GetAccessTokenResponse> in
// check http status code
switch response.1 {
case 200:
guard response.0?.accessToken != nil else {
return Observable.error(AuthenticationError.genericError)
}
// success
return Observable.just(response.0!)
case 400:
// invalid parameters, refresh token not existing
return Observable.error(AuthenticationError.invalidParameters)
case 404:
// user not existing
return Observable.error(AuthenticationError.userDoesntExist)
default:
// by default return network error
return Observable.error(AuthenticationError.networkError)
}
})
.retryWhen({ (errors) -> Observable<Void> in
return errors
.do(onNext: { (error) in
headers = [HeaderKeys.refreshToken.rawValue: "test test"]
})
.flatMap({error -> Observable<Int> in
debugLog("Retrying get refresh token")
if retryCounter >= maxRetryCounter {
let authError = error as? AuthenticationError ?? .genericError
if authError == AuthenticationError.invalidParameters {
// publish logged false on subject
VDAAuthenticationManager.shared.logged.onNext(false)
}
return Observable.error(error)
}
// increase the retry counter and retry
retryCounter += 1
return Observable<Int>.timer(delayRetry, scheduler: MainScheduler.instance)
})
.flatMap ({ (_) -> Observable<Void> in
return Observable.just(())
})
})
}

Answer 1

In the article RxSwift and Retrying a Network Request Despite Having an Invalid Token I explain how to keep and update a token and how to handle retries when you get a 401 error. Using deferred is part of the answer.
In your particular case. It looks like you could use my service like this:
func getToken(lastResponse: GetAccessTokenResponse?) -> Observable<(response: HTTPURLResponse, data: Data)> {
guard let refreshToken = lastResponse?.refreshToken else { return Observable.error(AuthenticationError.networkError) }
var request = URLRequest(url: CoreAPI.accessToken.url)
request.addValue(refreshToken, forHTTPHeaderField: HeaderKeys.refreshToken.rawValue)
return URLSession.shared.rx.response(request: request)
}
func extractToken(data: Data) throws -> GetAccessTokenResponse {
return try JSONDecoder().decode(GetAccessTokenResponse.self, from: data)
}
let tokenService = TokenAcquisitionService(initialToken: nil, getToken: getToken, extractToken: extractToken(data:))
In the above, you will have to pass a valid initialToken instead of nil or you will have to modify the getToken so it can get a token even if it doesn't have a refresh token.
An example of how to use deferred is below:
let response = Observable
.deferred { tokenAcquisitionService.token.take(1) }
.flatMap { makeRequest(withToken: $0) }
.map { response in
guard response.response.statusCode != 401 else { throw ResponseError.unauthorized }
return response
}
.retryWhen { $0.renewToken(with: tokenAcquisitionService) }
I explain in the article what each line of code is for and how it works.