Hidden SFViewController necessary for seamless user-auth on iOS 9 (https://library.launchkit.io/how-ios-9-s-safari-view-controller-could-completely-change-your-app-s-onboarding-experience-2bcf2305137f)

HiddenSFViewController.m

#import "SafariServices/SafariServices.h"

// Init SFViewController with webpage that'll use the
// app's URL scheme to send result back to app
NSURL *url = [NSURL URLWithString:@"http://api.app.com/determine-auth-state"];
SFSafariViewController *sfvc = [[SFSafariViewController alloc] initWithURL:url];

// Configure to be hidden over existing VC
sfvc.view.hidden = YES;
sfvc.modalPresentationStyle = UIModalPresentationOverCurrentContext;
 
// Present
[self presentViewController:sfvc animated:NO completion:^(){}];