Rails

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name: Rails slug: rails version: 1.0.1 description: Build reliable Rails apps avoiding ActiveRecord traps, N+1 queries, and callback pitfalls. metadata: {"clawdbot":{"emoji":"🛤️","requires":{"bins":["rails"]},"os":["linux","darwin","win32"]}}

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Quick Reference

| Topic | File | |-------|------| | N+1, callbacks, validations, scopes | activerecord.md | | Strong params, filters, render | controllers.md | | Route conflicts, constraints | routing.md | | Partials, helpers, caching, XSS | views.md | | ActiveJob, Sidekiq, retries | jobs.md | | Mass assignment, CSRF, SQL injection | security.md |

Critical Rules

save returns false on failure — save! raises, check return or use bang

update_all/delete_all skip callbacks and validations — data corruption if unaware

find_each for batches — Model.all.each loads entire table into memory

redirect_to doesn't halt execution — code after it runs, use and return

dependent: :destroy missing — orphan records accumulate forever

default_scope pollutes all queries including joins — almost always wrong

Callbacks chain silently — throw :abort stops save but returns false, not exception

includes without references in where string — N+1 still happens

||= memoization caches nil/false — use defined?(@var) ? @var : @var = compute

has_many through: vs has_and_belongs_to_many — latter has no join model for attrs

Nested before_action — multiple inheritance makes flow unreadable

render doesn't stop action — code continues, duplicate render crashes