Breaking Dependencies
The Visitor Design Pattern
The extensibility of code with new functionality is essential for long-term maintenance of a code base. However, when using dynamic polymorphism there is always a choice: either easily add types, or easily add operations. For instance, by means of inheritance hierarchies it's easy to add new types, but it's difficult to add new operations.
But there is a common workaround to overcome this weakness: the Visitor design pattern.
In this talk, I’ll explain the design properties of Visitor, including its benefits and shortcomings. I’ll also talk about different kinds of visitors (cyclic and acyclic) and show when to reach for a Visitor and when to avoid it. Additionally, I’ll demonstrate the different implementation strategies (classic and modern) and address their individual benefits and problems.
Klaus Iglberger
Klaus Iglberger is a freelance C++ trainer and consultant. He has finished his PhD in Computer Science in 2010 and since then is focused on large-scale C++ software design. He shares his expertise in popular advanced C++ courses around the world (mainly in Germany, but also in the rest of the EU and the US). Additionally, he is the initiator and lead designer of the Blaze C++ math library (https://bitbucket.org/blaze-lib/blaze/), one of the organizers of the Munich C++ user group (https://www.meetup.com/MUCplusplus/), and the organizer of the Back-to-Basics track at CppCon.