ruby

Ruby

Purpose

Write Ruby that stays readable as it grows: small objects with clear responsibilities, controllers that stay thin, and ActiveRecord queries that do not quietly issue a query per row.

When to Use

• Writing or reviewing Ruby and Rails code.
• Refactoring fat models or fat controllers.
• Diagnosing slow endpoints caused by ActiveRecord.
• Structuring an RSpec suite.
• Designing background jobs and their retry semantics.

Capabilities

• Object design: service objects, form objects, query objects, value objects.
• ActiveRecord: eager loading, scopes, batching, index-aware querying.
• Background processing with Sidekiq or Active Job, including idempotency.
• RSpec structure: request specs, model specs, factories, shared examples.
• RuboCop and Sorbet/RBS typing where valuable.

Inputs

• Application source, Gemfile, Rails version.
• Slow-query or profiling data when performance is the concern.

Outputs

• Controllers that authenticate, authorize, delegate, and render — nothing else.
• Named scopes and eager-loaded queries with no N+1.
• Specs that describe behavior rather than restate implementation.

Workflow

1. Locate the responsibility — If a method touches HTTP, business rules, and persistence, split it before changing it.
2. Extract a service object — One public call, explicit dependencies, no global state.
3. Fix the queries — Add includes, convert loops into set operations, batch with find_each.
4. Make jobs idempotent — Retries are guaranteed; double-execution must be harmless.
5. Gate — RSpec, RuboCop, and Bullet (or equivalent) to fail the build on N+1.

Best Practices

• Controllers do not contain business logic. If a controller action exceeds ten lines, extract.
• Callbacks (after_save, before_create) create action at a distance. Prefer explicit service calls.
• Use find_each for anything that could exceed a few thousand rows; all.each loads the table into memory.
• Every background job should be safe to run twice. Key the side effect, not the invocation.
• rescue => e without re-raising swallows bugs. Rescue the specific class.
• Freeze constants and prefer immutable value objects for domain concepts.