+[NSObject cast:]

gistfile1.m

@interface NSObject (Cast)
+ (instancetype)cast:(id)from;
@end

@implementation NSObject (Cast)
+ (instancetype)cast:(id)from {
    if ([from isKindOfClass:self]) {
        return from;
    }
    return nil;
}
@end

The usage here is basically this, right?

UIButton *someButton = [UIButton new];
UIView *buttonView = [UIView cast:someButton];

That's backwards. You don't need a cast to assign a UIButton value to a UIView. It's more like

UIButton *button = [UIButton cast:someView];
if (button != nil) {
    // someView was a button
}