Facebook SDK 3.1 iOS: Handle login if user remove app from Facebook Settings

I found this happening to myself as well.... It was discovered when a user changed their facebook password, and we could no longer authenticate. Doing a manual resync / clear of the account session allowed them to login again.

-(void)syncFacebookAccount {    [self forceLogout];    ACAccountStore *accountStore = [[ACAccountStore alloc] init];    ACAccountType *accountTypeFB = [accountStore         accountTypeWithAccountTypeIdentifier:@"com.apple.facebook"];    if (accountStore && accountTypeFB) {    NSArray *fbAccounts = [accountStore accountsWithAccountType:accountTypeFB];    id account;    if (fbAccounts && [fbAccounts count] > 0 && (account = [fbAccounts objectAtIndex:0])) {    [accountStore renewCredentialsForAccount:account completion:^(ACAccountCredentialRenewResult renewResult, NSError *error) {                    // Not actually using the completion handler...    }];            }        }    }

It's actually VERY hard to parse out and detect these types of errors for two reasons:

1. I cannot figure out any way to detect this problem until you actually attempt and fail an FBRequest (or similar), and
2. The NSError object passed from the failed FBRequest is ABSURDLY difficult to parse and use in any functional way.

Below is the crazy method I wrote while literally pulling an all-nighter to deal with this. It handles the NSError *error object from the failed FBRequest attempt, and passes it to the relevant methods OR displays the most sensible error I could find (or hits the bottom catch-all).

Note the comments - particularly around innerError and parsedResponse - that detail what I've discovered so far. Good luck, brave soldier:

- (void)handleFacebookError:(NSError *)error         withPermissionType:(RMFacebookPermissionsType)type // this is just a typedef enum specifying Write or Read permissions so I can react accordingly             withCompletion:(void (^)(BOOL retry))completionBlock {    newMethodDebugLog;    NSParameterAssert(error);    NSParameterAssert(type);    NSParameterAssert(completionBlock); //  the completion block tells the controller whether the error is 'fatal' or can be recovered - if YES, it can be recovered    // this is the parsed result of the graph call; some errors can appear here, too, sadly    NSDictionary *parsedResponse = [error.userInfo objectForKey:@"com.facebook.sdk:ParsedJSONResponseKey"];    int parsedErrorCode = [[[[parsedResponse objectForKey:@"body"]                             objectForKey:@"error"]                            objectForKey:@"code"]                           intValue];    // this is an instance of NSError created by Facebook; it contains details about the error    NSError *innerError = [error.userInfo objectForKey:@"com.facebook.sdk:ErrorInnerErrorKey"];    // innerError is usually un-recoverable    if (innerError) {        // innerError seems to be the response given in true HTTP problems;        DebugLog(@"______innerError FOUND______");        DebugLog(@"innerError: %@",innerError);        DebugLog(@"innerError.code: %d",innerError.code);        // digging deep enough, you can actually find a coherent error message! :D        DebugLog(@"innerError.localizedDescription: %@",innerError.localizedDescription);        if (![alert isVisible]) {            NSString *errorString = @"Facebook Connection Failed";            NSString *okString = @"OK";            alert = [[UIAlertView alloc] initWithTitle:errorString                                               message:innerError.localizedDescription                                              delegate:nil                                     cancelButtonTitle:okString                                     otherButtonTitles:nil];            [alert show];        } else {            DebugLog(@"Alert already showing!");        }        completionBlock(NO);    } else if (parsedResponse &&               parsedErrorCode != 2) { // I honestly forget what error 2 is.. documentation fail :(        // parsedResponses can usually be recovered        DebugLog(@"parsed response values: %@",[parsedResponse allValues]);        switch (parsedErrorCode) {            case 2500:            case 200:            case 190:            {                DebugLog(@"parsedError code hit! forcing re-login.");                // all errors in case 190 seem to be OAuth issues                // http://fbdevwiki.com/wiki/Error_codes#Parameter_Errors                // if needed, "error_subcode" 458 == user has de-authorized your app                // case 2500 reported while grabbing from a photo album & not logged in                // case 200 "requires extended permission: publish_actions"                if (type == RMFacebookPermissionsTypeRead) {                    [self _getFacebookReadPermissionsWithUI:YES                                                 completion:completionBlock];                } else if (type == RMFacebookPermissionsTypeWrite) {                    [self _getFacebookWritePermissionsWithUI:YES                                                  completion:completionBlock];                }                break;            }            default:                completionBlock(YES);                break;        }    } else {        if (![alert isVisible]) {            NSString *errorString = @"Facebook Error";            NSString *messageString = @"Mixture Photos was unable to connect to Facebook on your behalf. This is usually a temporary problem. Please try again later.";            NSString *okString = @"OK";            alert = [[UIAlertView alloc] initWithTitle:errorString                                               message:messageString                                              delegate:nil                                     cancelButtonTitle:okString                                     otherButtonTitles:nil];            [alert show];        } else {            DebugLog(@"Alert already showing!");        }        completionBlock(NO);    }}

I have the same problem and could not find proper documentation about error codes on Facebook SDK site.

I solved problem by comparing the [error code]; or [error userInfo]; value.

Your session will have the state FBSessionStateClosedLoginFailed and userInfo dictionary of error will have the following form

"com.facebook.sdk:ErrorLoginFailedReason" = "com.facebook.sdk:ErrorLoginFailedReason";

On the other hand error code shows me 2 so that you can handle it at the end of sessionStateChanged::: function

- (void)sessionStateChanged:(FBSession *)session                  state:(FBSessionState)state                  error:(NSError *)error {switch (state) {    case FBSessionStateOpen: {        //update permissionsArrat        [self retrieveUSerPermissions];        if (!needstoReopenOldSession) {            //First User information            [self getUserInformation:nil];        }        NSNotification *authorizationNotification = [NSNotification notificationWithName:facebookAuthorizationNotification object:nil];        [[NSNotificationCenter defaultCenter] postNotification:authorizationNotification];    }    case FBSessionStateClosed: {        break;    }    case FBSessionStateClosedLoginFailed: {        [FBSession.activeSession closeAndClearTokenInformation];        break;    }    default:        break;}if (error) {    NSNotification *authorizationNotification = [NSNotification  notificationWithName:faceBookErrorOccuredNotification object:error];    [[NSNotificationCenter defaultCenter] postNotification:authorizationNotification];}}