What are the reasons that presentShareDialog returns nil?

Question

I'm trying to allow the user to post a simple Facebook status update, without using OpenGraph. So far, allowing the user to log in and asking for publish_actions permissions, goes well without a hitch.

However, when I try to call presentShareDialogWithLink:name:caption:description:picture:clientState:handler: it always returns nil and shows nothing. It doesn't even appear to call the handler, which leaves at a loss as to why it doesn't work.

What are the reasons that this can fail? If I knew what might be the reason, I can always retrace my steps.

Relevant code

User presses the button

AppDelegate_Pad *appDelegate = (AppDelegate_Pad *)[[UIApplication sharedApplication] delegate];
if(FBSession.activeSession.isOpen) {
    [appDelegate postFacebookUpdateWithAlbum:album];
} else {
    // The person using the app has initiated a login, so call the openSession method
    // and show the login UX if necessary.
    [appDelegate openSessionWithAllowLoginUI:YES album:album];
}

Facebook code in App Delegate

- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation
{
    if ([FBSession.activeSession handleOpenURL:url]) {
        [self postFacebookUpdateWithAlbum:self.facebookAlbum];
        self.facebookAlbum = nil;
        return  YES;
    }
}

#pragma mark Facebook

    /*
     * Opens a Facebook session and optionally shows the login UX.
     */
    - (BOOL)openSessionWithAllowLoginUI:(BOOL)allowLoginUI album:(LPAlbum *)album {
        self.facebookAlbum = album;

        return [FBSession openActiveSessionWithPublishPermissions:@[@"publish_actions"] defaultAudience:FBSessionDefaultAudienceFriends allowLoginUI:allowLoginUI completionHandler:^(FBSession *session, FBSessionState status, NSError *error) {
            [self sessionStateChanged:session
                                state:status
                                error:error];

        }];
    }

    - (void)postFacebookUpdateWithAlbum:(LPAlbum *)album {
        if (album) {
            // we defer request for permission to post to the moment of post, then we check for the permission
            if ([FBSession.activeSession.permissions indexOfObject:@"publish_actions"] == NSNotFound) {
                // if we don't already have the permission, then we request it now
                [FBSession.activeSession requestNewPublishPermissions:@[@"publish_actions"]
                                                      defaultAudience:FBSessionDefaultAudienceFriends
                                                    completionHandler:^(FBSession *session, NSError *error) {
                                                        if (!error) {
                                                            [self doPostWithAlbum:album];
                                                        }
                                                        else {
                                                            DLog(@"Could not get permissions. Error: %@", error);
                                                        }
                                                    }];
            } else {
                [self doPostWithAlbum:album];
            }
        }
    }

    - (void)doPostWithAlbum:(LPAlbum *)album {
        NSString *initialText = [NSString stringWithFormat:@"Neat status update"];
        NSURL *coverImageURL = [NSURL URLWithString:album.imageBaseURLString];
        UIImage *coverImage = [UIImage imageWithContentsOfFile:album.imageBaseURLString];
        NSURL *infoLinkURL = [NSURL URLWithString:album.infoSiteURLString];

        // First, try the iOS 6 native sharing.
        BOOL iOS6native = [FBDialogs presentOSIntegratedShareDialogModallyFrom:self.window.rootViewController initialText:initialText image:coverImage url:infoLinkURL handler:^(FBOSIntegratedShareDialogResult result, NSError *error) {
        }];

        if (!iOS6native) {
            NSString *name = @"name";
            NSString *caption = @"caption";
            NSString *description = @"description";

            FBShareDialogParams *params = [[FBShareDialogParams alloc] init];
            params.link = infoLinkURL;
            params.name = name;
            params.description = description;

            BOOL canPresent = [FBDialogs canPresentShareDialogWithParams:params]; // returns NO
            DLog(@"Can present with params? %@", canPresent ? @"Yes" : @"No");
            canPresent = [FBDialogs canPresentOSIntegratedShareDialogWithSession:[FBSession activeSession]]; // returns NO
            DLog(@"Can present with session? %@", canPresent ? @"Yes" : @"No");

            FBAppCall *appCall = [FBDialogs presentShareDialogWithLink:infoLinkURL
                                                                  name:name
                                                               caption:caption
                                                           description:description
                                                               picture:coverImageURL
                                                           clientState:nil
                                                               handler:^(FBAppCall *call, NSDictionary *results, NSError *error) {
                                                                   if (error) {
                                                                       DLog(@"Error: %@", error.description);
                                                                   } else {
                                                                       DLog(@"Success!");
                                                                   }
                                                               }];
            if (!appCall) {
                // App call failed.
            }
        }
    }

    // Convenience method to perform some action that requires the "publish_actions" permissions.
    - (void) performPublishAction:(void (^)(void)) action {
        // we defer request for permission to post to the moment of post, then we check for the permission
        if ([FBSession.activeSession.permissions indexOfObject:@"publish_actions"] == NSNotFound) {
            // if we don't already have the permission, then we request it now
            [FBSession.activeSession requestNewPublishPermissions:@[@"publish_actions"]
                                                  defaultAudience:FBSessionDefaultAudienceFriends
                                                completionHandler:^(FBSession *session, NSError *error) {
                                                    if (!error) {
                                                        action();
                                                    }
                                                    //For this example, ignore errors (such as if user cancels).
                                                }];
        } else {
            action();
        }

    }

Answer 1

presentShareDialogWithLink requires the Facebook app (it's documented here, and says "Presents a dialog in the Facebook application ...").

If you want to use the iOS6 system dialog, you want one of the presentOSIntegratedShareDialogModallyFrom methods, like this one.