Custom Back Button And Swipe Back. The only nice way I found to actually completely override the back button is to set the leftBarButtonItem, but then the swipe back gesture breaks. Luckily it's an easy fix when you know how

CustomBackButton.m

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                             initWithImage:img
                                             style:UIBarButtonItemStylePlain
                                             target:self
                                             action:@selector(onBack:)];
    self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self;