Chapter 4. Data abstractions
This chapter covers
- Abstracting with modules
- Working with hierarchical data
- Polymorphism with protocols
This chapter deals with building higher-level data structures. In any complex system, there will be a need for abstractions such as Money, Date, Employee, and OrderItem, all textbook examples of higher-level abstractions that usually aren’t directly supported by the language and are instead written on top of built-in types.
In Elixir, such abstractions are implemented with pure, stateless modules. In this chapter, you’ll learn how to create and work with your own data abstractions.
In a typical OO language, the basic abstraction building blocks are classes and objects. For example, there may be a String class available that implements various string operations. Each string is then an instance of that class that can be manipulated by calling methods, as the following Ruby snippet illustrates:
This approach generally isn’t used in Elixir. Being a functional language, Elixir promotes decoupling of data from the code. Instead of classes, you use modules, which are collection of functions. Instead of calling methods on objects, you explicitly call module functions and provide input data via arguments. The following snippet shows the Elixir way of uppercasing the string: