law-of-demeter

Identify the chain's purpose, then add a purpose-named delegation method on the outermost object that delegates through each intermediate level. For example, replace `order.getCustomer().getAddress().getCity()` with `order.getShippingCity()`, adding delegation methods on Order and Customer.

A Train Wreck is a chained call like `a.getB().getC().doX()` that traverses an object's internal structure. It violates the Law of Demeter because the caller depends on friends of friends, making the code brittle to structural changes.

No, fluent APIs and builder patterns are explicit exceptions because each method returns the same object, so you keep talking to the same friend. Stream operations, DTO field access, and same-type standard library chains like `text.strip().lower()` are also allowed.

The refactoring patterns cover Java, Kotlin, Scala, TypeScript, Python, Ruby, Go, and Rust. Each language section shows delegation methods, plus idiomatic tools like Rails delegate, Go interfaces, Rust traits, and Scala type classes.

Avoid over-application when it causes a delegation method explosion, typically more than three delegation methods per class. That signals a design problem better solved by rethinking responsibility allocation rather than wrapping every field.

Optional chaining like `user?.address?.city` prevents null errors but still exposes internal structure, so the coupling violation remains. Hide the traversal behind a delegation method such as `user.getCity()` that handles the nullability internally.