-[UIViewController viewWillAppear:] from UIView

gistfile1.m

- (void)tapIntoViewControllerWillAppear {
  @weakify(self);
  [[[[[[[RACSignal interval:0.1f onScheduler:[RACScheduler mainThreadScheduler]] takeUntil:self.rac_willDeallocSignal] flattenMap:^RACStream *(id value) {
    @strongify(self);
    
    return [RACSignal return:self.pb_viewController];
  }] ignore:nil] take:1] flattenMap:^RACStream *(UIViewController *viewController) {
    return [viewController rac_signalForSelector:@selector(viewWillAppear:)];
  }] subscribeNext:^(id x) {
    @strongify(self);
    
    // Do something
  }];
}

gistfile2.m

@implementation UIView (PBViewControllerFromView)

- (UIViewController *)pb_viewController {
  return [self valueForKey:@"_viewDelegate"] ?: self.superview.pb_viewController;
}

@end