ReactiveCocoa-way to present UIViewControllers

UIViewController+RAC.m

@implementation UIViewController (RAC)

- (RACCommand *)showCommandWithPresenter:(RACSignal *)presenter {
    RACSignal *presentedControllerDataSignal = [RACSignal return:self];
    return [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) {
        RACSignal *presentDataSignal = [presenter combineLatestWith:presentedControllerDataSignal];
        return [presentDataSignal.deliverOnMainThread flattenMap:^RACStream *(RACTuple *tuple) {
            return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
                UIViewController *presenterController = tuple.first;
                UIViewController *controllerToPresent = tuple.second;
                [presenterController presentViewController:controllerToPresent animated:YES completion:^{
                    [subscriber sendNext:[RACUnit defaultUnit]];
                    [subscriber sendCompleted];
                }];
                
                return nil;
            }];
        }];
    }];
}

@end