Recently, I've gotten back into iOS Development. One of the UI elements that I've thought about adding a good few times is a popup view controller, so I went ahead and made it.

To make the popup view controller, I added a category on UIViewController. I added two basic methods to present and dismiss the popup view controller.

Presenting the popup view controller:

- (void)presentPopupViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag completion:(void (^)(void))completion {
    // setup
    self.popupViewController = viewControllerToPresent;
    CGRect frame = viewControllerToPresent.view.frame;
    CGFloat x = ([UIScreen mainScreen].bounds.size.width - viewControllerToPresent.view.frame.size.width)/2;
    CGFloat y =([UIScreen mainScreen].bounds.size.height - viewControllerToPresent.view.frame.size.height)/2;
    CGRect finalFrame = CGRectMake(x, y, frame.size.width, frame.size.height);
    // shadow setup
    viewControllerToPresent.view.layer.shadowOffset = CGSizeMake(0.0f, 0.0f);
    viewControllerToPresent.view.layer.shadowColor = [UIColor blackColor].CGColor;
    viewControllerToPresent.view.layer.shadowRadius = 3.0f;
    viewControllerToPresent.view.layer.shadowOpacity = 0.8f;
    viewControllerToPresent.view.layer.shadowPath = [UIBezierPath bezierPathWithRect:viewControllerToPresent.view.layer.bounds].CGPath;
    // rounded corners
    viewControllerToPresent.view.layer.cornerRadius = 5.0f;
    // black uiview
    UIView *fadeView = [UIView new];
    fadeView.frame = [UIScreen mainScreen].bounds;
    fadeView.backgroundColor = [UIColor blackColor];
    fadeView.alpha = 0.0f;
    [self.view addSubview:fadeView];
    objc_setAssociatedObject(self, &CWFadeViewKey, fadeView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (flag) { // animate
        CGRect initialFrame = CGRectMake(finalFrame.origin.x, [UIScreen mainScreen].bounds.size.height + 10, finalFrame.size.width, finalFrame.size.height);
        viewControllerToPresent.view.frame = initialFrame;
        [self.view addSubview:viewControllerToPresent.view];
        [UIView animateWithDuration:ANIMATION_TIME delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
            viewControllerToPresent.view.frame = finalFrame;
            fadeView.alpha = FADE_ALPHA;
        } completion:^(BOOL finished) {
            [completion invoke];
        }];
    } else { // don't animate
        viewControllerToPresent.view.frame = finalFrame;
        [self.view addSubview:viewControllerToPresent.view];
        [completion invoke];
    }
}

Dismissing the popup view controller:

- (void)dismissPopupViewControllerAnimated:(BOOL)flag completion:(void (^)(void))completion {
    UIView *fadeView = objc_getAssociatedObject(self, &CWFadeViewKey);
    if (flag) { // animate
        CGRect initialFrame = self.popupViewController.view.frame;
        [UIView animateWithDuration:ANIMATION_TIME delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
            self.popupViewController.view.frame = CGRectMake(initialFrame.origin.x, [UIScreen mainScreen].bounds.size.height, initialFrame.size.width, initialFrame.size.height);
            fadeView.alpha = 0.0f;
        } completion:^(BOOL finished) {
            [self.popupViewController.view removeFromSuperview];
            [fadeView removeFromSuperview];
            self.popupViewController = nil;
            [completion invoke];
        }];
    } else { // don't animate
        [self.popupViewController.view removeFromSuperview];
        [fadeView removeFromSuperview];
        self.popupViewController = nil;
        fadeView = nil;

        [completion invoke];
    }
}

Because there is an option to dismiss without animation, it is also possible to implement custom dismissal animations as well as gesture-based dismissal. You can find the project on my GitHub page.