UIButton set touch handler in code

One option is to set the button up using

[myButton addTarget:yourOtherClass action:@selector(mySelector:) forControlEvents:UIControlEventTouchUpInside];

but this is a bit dangerous because target is not retained so you could send the message to a deallocated object.

You could instead set up a protocol

PopupViewController.h

#import <UIKit/UIKit.h>

@class PopupViewController;

@protocol PopupViewControllerDelegate
- (void)viewController:(PopupViewController *)controller viewTapped:(UIView *)view;
@end

@interface PopupViewController : UIViewController

@property (nonatomic, assign) NSObject<PopupViewControllerDelegate> *delegate;

- (IBAction)viewTapped:(UIView *)view;

@end

Then in your implementation

PopupViewController.m

- (IBAction)viewTapped:(UIView *)view {
    if (!self.delegate) return;
    if ([self.delegate respondsToSelector:@selector(viewController:viewTapped:)]) {
        [self.delegate viewController:self viewTapped:view];
    }
}

As the method defined in the protocol was not optional I could have instead done a check for (self.delegate) to make sure it is set instead of respondsToSelector.