Notes on ‘Layered Design for RoR Apps’ book

Chapter 1

Chapter 2

Chapter 3

Adapter vs Plugin vs Wrapper patterns

 The key difference between adapters and plugins is that plugins provide additional functionality, not just an expected interface.  The wrapper pattern could be seen as a degenerate case of the adapter pattern. With a wrapper object, we have both an application-level interface and the implementation encapsulation. Wrappers are usually much easier to deal with in tests than implementations.

Chapter 4 - Rails Anti-Patterns

• Callbacks, callbacks everywhere
• Concerning Rails concerns
• On global and current states

  can quickly turn into anti-patterns, since they tend to cross the boundaries between layers and lead to code that attracts many responsibilities

Chapter 5

Chapter 6

Chapter 13

Infra level parts: • Database adapters • Third-party API clients • Caching and storage systems (that is, Active Storage backends) • Configuration providers (credentials, secrets, and so on) • Background processing engines (for example, Sidekiq and GoodJob) • Web servers (for example, Puma and Unicorn) and Rack middleware • Logging and monitoring tools

The abstraction distance (the number of in-between abstractions before we reach the actual implementation) can be big in Rails.

 > implementations are not owned by our application or the framework, while infrastructure abstractions are. i.e.  > ActiveRecord::Base.connection - still not the actual database connection wrapper (which is database-specific) but, instead, an infrastructure abstraction provided by the framework.