Chapter 13: Advanced Macro Usages
In the last few chapters, we have looked at various metaprogramming concepts, such as macros, annotations, and how they can be used together to allow for introspecting types, methods, and instance variables at compile time. However, for the most part, we used them independently. These concepts can also be combined in order to allow for the creation of even more powerful patterns! In this chapter, we are going to explore a few of these, including:
- Using annotations to influence runtime logic
- Exposing annotation/type data at runtime
- Determining a constant's value at compile time
- Creating custom compile-time errors
By the end of this chapter, you should have a deeper understanding of metaprogramming in Crystal. You should also have some ideas of the non-directly apparent use cases for metaprogramming that will allow you to create unique solutions to problems in your application.