In this chapter, we will see the next three Behavioral design patterns. The difficulty is being raised as now we will use combinations of Structural and Creational patterns to better solve the objective of some of the Behavioral patterns.
We will start with Template design pattern, a pattern that looks very similar to the Strategy pattern but that provides greater flexibility. Memento design pattern is used in 99% of applications we use every day to achieve undo functions and transactional operations. Finally, we will write a reverse polish notation interpreter to perform simple mathematical operations.
Let's start with the Template design pattern.