Double Application Of Smart Pointers

In my reading, I came across a cool, little technique in C++ which allows us to invoke a pre-method and a post-method automatically when a member method of the class is called. It makes use of so called "Double Application Of Smart Pointers" (see the second bullet).

This technique might be useful to implement different popular things such as pre-conditions and post-conditions, the "Monitor Object" pattern (POSA2), pointcut models in AOP, the Decorator pattern (GOF) and also the Execute-Around-Method pattern.