how to refresh an oauth token when using the Facebook iPhone SDK

Question

I\'m using the Facebook SDK for iOS in my app: http://github.com/facebook/facebook-ios-sdk

The oAuth token expires after about 2 hours. How can I \"refresh\" the oAuth

Answer 1

As of today Facebook is supposed to refresh tokens automatically, requests to GraphAPI can be done without providing token string either (Facebook handles it under the hood).

Moreover, if it happens that user wasn't using app for a long time and his token managed to expire, on your next request to Graph API an alert will be shown by Facebook's SDK asking user to relogin (all that is handled by Facebook and when done - will return into FBSDKGraphRequest's closure).

However, if someone really has a reason to manually refresh access token, here's an example (Swift 4):

private var selfDestructableNotificationToken: NotificationTokenThatAutomaticallyRemovesObserver?
final class NotificationTokenThatAutomaticallyRemovesObserver: NSObject { // more info here: https://oleb.net/blog/2018/01/notificationcenter-removeobserver/
    let token: Any
    init(_ token: Any) { self.token = token }
    deinit { NotificationCenter.default.removeObserver(token) }
}

...

if let currentFBToken = FBSDKAccessToken.current() { // if this is a Facebook user, not an email-based user
    if FBSDKAccessToken.currentAccessTokenIsActive() { // and his token has not expired yet
        let token = NotificationCenter.default.addObserver(forName: NSNotification.Name.FBSDKAccessTokenDidChange, object: nil, queue: OperationQueue.main) { notification in
            if let userInfo = notification.userInfo, let refreshedToken = userInfo["FBSDKAccessToken"] as? FBSDKAccessToken {
                self.fbAccessToken = refreshedToken.tokenString
            } else {
                self.fbAccessToken = currentFBToken.tokenString // falling back to using an old token (better than none)
            }
        }
        self.selfDestructableNotificationToken = NotificationTokenThatAutomaticallyRemovesObserver(token)
        FBSDKAccessToken.refreshCurrentAccessToken { _, _, error in
            if let error = error {
                print("failed to refresh Facebook token with error \(error.localizedDescription)")
                self.fbAccessToken = currentFBToken.tokenString // falling back to an old token (better than none)
            }
        }
    } else if FBSDKAccessToken.current().isExpired { // unlucky user. Probably returned to the app after > 2 months break
        self.fbAccessToken = currentFBToken.tokenString // assigning expired token. Facebook will ask user to relogin as soon as we call Graph API with that expired token
    }
}