Alamofire 5 Adapting and Retrying Requests

Question

I am trying to implement my OAuth2 flow using Alamofire 5.0.0-beta.3. As i can see the documentation is still for Alamofire 4 as stated in the github page as well.

I am trying to make the Oauth2 handler following the documentation for Alamofire 4. As the class names are changed, I am completely lost while making it.

This is the code that i am following:

class OAuth2Handler: RequestAdapter, RequestRetrier {
    private typealias RefreshCompletion = (_ succeeded: Bool, _ accessToken: String?, _ refreshToken: String?) -> Void

    private let sessionManager: SessionManager = {
        let configuration = URLSessionConfiguration.default
        configuration.httpAdditionalHeaders = SessionManager.defaultHTTPHeaders

        return SessionManager(configuration: configuration)
    }()

    private let lock = NSLock()

    private var clientID: String
    private var baseURLString: String
    private var accessToken: String
    private var refreshToken: String

    private var isRefreshing = false
    private var requestsToRetry: [RequestRetryCompletion] = []

    // MARK: - Initialization

    public init(clientID: String, baseURLString: String, accessToken: String, refreshToken: String) {
        self.clientID = clientID
        self.baseURLString = baseURLString
        self.accessToken = accessToken
        self.refreshToken = refreshToken
    }

    // MARK: - RequestAdapter

    func adapt(_ urlRequest: URLRequest) throws -> URLRequest {
        if let urlString = urlRequest.url?.absoluteString, urlString.hasPrefix(baseURLString) {
            var urlRequest = urlRequest
            urlRequest.setValue("Bearer " + accessToken, forHTTPHeaderField: "Authorization")
            return urlRequest
        }

        return urlRequest
    }

    // MARK: - RequestRetrier

    func should(_ manager: SessionManager, retry request: Request, with error: Error, completion: @escaping RequestRetryCompletion) {
        lock.lock() ; defer { lock.unlock() }

        if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 {
            requestsToRetry.append(completion)

            if !isRefreshing {
                refreshTokens { [weak self] succeeded, accessToken, refreshToken in
                    guard let strongSelf = self else { return }

                    strongSelf.lock.lock() ; defer { strongSelf.lock.unlock() }

                    if let accessToken = accessToken, let refreshToken = refreshToken {
                        strongSelf.accessToken = accessToken
                        strongSelf.refreshToken = refreshToken
                    }

                    strongSelf.requestsToRetry.forEach { $0(succeeded, 0.0) }
                    strongSelf.requestsToRetry.removeAll()
                }
            }
        } else {
            completion(false, 0.0)
        }
    }

    // MARK: - Private - Refresh Tokens

    private func refreshTokens(completion: @escaping RefreshCompletion) {
        guard !isRefreshing else { return }

        isRefreshing = true

        let urlString = "\(baseURLString)/oauth2/token"

        let parameters: [String: Any] = [
            "access_token": accessToken,
            "refresh_token": refreshToken,
            "client_id": clientID,
            "grant_type": "refresh_token"
        ]

        sessionManager.request(urlString, method: .post, parameters: parameters, encoding: JSONEncoding.default)
            .responseJSON { [weak self] response in
                guard let strongSelf = self else { return }

                if 
                    let json = response.result.value as? [String: Any], 
                    let accessToken = json["access_token"] as? String, 
                    let refreshToken = json["refresh_token"] as? String 
                {
                    completion(true, accessToken, refreshToken)
                } else {
                    completion(false, nil, nil)
                }

                strongSelf.isRefreshing = false
            }
    }
}

This is how to use this for alamofire 4:

let baseURLString = "https://some.domain-behind-oauth2.com"

let oauthHandler = OAuth2Handler(
    clientID: "12345678",
    baseURLString: baseURLString,
    accessToken: "abcd1234",
    refreshToken: "ef56789a"
)

let sessionManager = SessionManager()
sessionManager.adapter = oauthHandler
sessionManager.retrier = oauthHandler

let urlString = "\(baseURLString)/some/endpoint"

sessionManager.request(urlString).validate().responseJSON { response in
    debugPrint(response)
}

This is the link i am following to implement this. https://github.com/Alamofire/Alamofire/blob/master/Documentation/AdvancedUsage.md#adapting-and-retrying-requests

Answer 1

Look at something like this.

 struct EnvironmentInterceptor: RequestInterceptor {

    func adapt(_ urlRequest: URLRequest, for session: Session, completion: @escaping (Result<URLRequest>) -> Void) {
        var adaptedRequest = urlRequest
        guard let token = AtraqService.shared.user?.token.accessToken else {
        completion(.success(adaptedRequest))
        return
        }
        adaptedRequest.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        completion(.success(adaptedRequest))
     }

     func retry(_ request: Request, for session: Session, dueTo error: Error, completion: @escaping (RetryResult) -> Void) {
        if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 {
        //get token
        }
    }
}

Then

        Session(configuration: configuration,  interceptor: EnvironmentInterceptor())

Finally

request().validate().response...

Answer 2

If Alamofire 5 is not intercepting (adapting or retrying) your requests for some reason, then just try to check the delegate signature out as described here.

func adapt(_ urlRequest: URLRequest, for session: Session, completion: @escaping (AFResult<URLRequest>) -> Void) {
    var modifiedURLRequest = urlRequest
    let apiToken = config.apiToken
    modifiedURLRequest.setValue(apiToken, forHTTPHeaderField: Constants.apiTokenHeader)
    completion(.success(modifiedURLRequest))
}

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

Here's the difference (look at the signature):

func adapt(_ urlRequest: URLRequest, for session: Alamofire.Session, completion: @escaping (AFResult<URLRequest>) -> Void) {
    var modifiedURLRequest = urlRequest
    let apiToken = config.apiToken
    modifiedURLRequest.setValue(apiToken, forHTTPHeaderField: Constants.apiTokenHeader)
    completion(.success(modifiedURLRequest))
}

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