A deep dive into how SOLID principles translate to Ruby, drawing on Jeremy Evans' 'Polished Ruby Programming'. Each principle is reframed through Ruby's open classes, duck typing, and pragmatic design culture. SRP becomes about cohesion and volatility rather than class size. OCP is about making expected change easy without editing fragile code, not enforcing immutability. LSP shifts from inheritance hierarchies to honoring behavioral protocols. ISP becomes an API surface-area and cohesion problem rather than a type-system concern. DIP is reframed as demand-driven injection of genuinely volatile dependencies, not blanket abstraction. Concrete Ruby and Rails code examples illustrate each reinterpretation, including a detailed walkthrough of dependency injection trade-offs in a CurrentDay class.
