Exploring Functional Domain Modeling in Elixir

The article discusses how functional modeling techniques can improve Elixir code. It utilizes a use case from a Library domain to illustrate common pitfalls in Elixir codebases and proposes a functional approach to address these issues. The author provides code examples contrasting traditional and functional styles and highlights the coupling between modules, mixing of concerns, and input issues in conventional approaches. The article emphasizes the benefits of using pure functions and immutable types to concentrate on domain logic, outlining how to implement this through positional arguments and condition handling in function bodies. It describes the 'functional sandwich' technique, where pure domain logic forms the core of the approach, separated from data fetching and persistence concerns. The separation ensures that changes in one area (data sources, requirements) don't affect others. The service layer, encapsulating these pure functions, simplifies testing and focuses on domain logic. The author advocates for this functional design as more testable, maintainable, and appealing than traditional approaches.