Rails Expert

Rails Expert

Core Workflow

1. Analyze requirements — Identify models, routes, real-time needs, background jobs
2. Scaffold resources — rails generate model User name:string email:string, rails generate controller Users
3. Run migrations — rails db:migrate and verify schema with rails db:schema:dump
   • If migration fails: inspect db/schema.rb for conflicts, rollback with rails db:rollback, fix and retry
4. Implement — Write controllers, models, add Hotwire (see Reference Guide below)
5. Validate — bundle exec rspec must pass; bundle exec rubocop for style
   • If specs fail: check error output, fix failing examples, re-run with --format documentation for detail
   • If N+1 queries surface during review: add includes/eager_load (see Common Patterns) and re-run specs
6. Optimize — Audit for N+1 queries, add missing indexes, add caching

Reference Guide

Load detailed guidance based on context:

Common Patterns

N+1 Prevention with includes/eager_load

# BAD — triggers N+1
posts = Post.all
posts.each { |post| puts post.author.name }

# GOOD — eager load association
posts = Post.includes(:author).all
posts.each { |post| puts post.author.name }

# GOOD — eager_load forces a JOIN (useful when filtering on association)
posts = Post.eager_load(:author).where(authors: { verified: true })

Turbo Frame Setup (partial page update)

<%# app/views/posts/index.html.erb %>
<%= turbo_frame_tag "posts" do %>
  <%= render @posts %>
  <%= link_to "Load More", posts_path(page: @next_page) %>
<% end %>

<%# app/views/posts/_post.html.erb %>
<%= turbo_frame_tag dom_id(post) do %>
  <h2><%= post.title %></h2>
  <%= link_to "Edit", edit_post_path(post) %>
<% end %>

# app/controllers/posts_controller.rb
def index
  @posts = Post.includes(:author).page(params[:page])
  @next_page = @posts.next_page
end

Sidekiq Worker Template

# app/jobs/send_welcome_email_job.rb
class SendWelcomeEmailJob < ApplicationJob
  queue_as :default
  sidekiq_options retry: 3, dead: false

  def perform(user_id)
    user = User.find(user_id)
    UserMailer.welcome(user).deliver_now
  rescue ActiveRecord::RecordNotFound => e
    Rails.logger.warn("SendWelcomeEmailJob: user #{user_id} not found — #{e.message}")
    # Do not re-raise; record is gone, no point retrying
  end
end

# Enqueue from controller or model callback
SendWelcomeEmailJob.perform_later(user.id)

Strong Parameters (controller template)

# app/controllers/posts_controller.rb
class PostsController < ApplicationController
  before_action :set_post, only: %i[show edit update destroy]

  def create
    @post = Post.new(post_params)
    if @post.save
      redirect_to @post, notice: "Post created."
    else
      render :new, status: :unprocessable_entity
    end
  end

  private

  def set_post
    @post = Post.find(params[:id])
  end

  def post_params
    params.require(:post).permit(:title, :body, :published_at)
  end
end

Constraints

MUST DO

• Prevent N+1 queries with includes/eager_load on every collection query involving associations
• Write comprehensive specs targeting >95% coverage
• Use service objects for complex business logic; keep controllers thin
• Add database indexes for every column used in WHERE, ORDER BY, or JOIN
• Offload slow operations to Sidekiq — never run them synchronously in a request cycle

MUST NOT DO

• Skip migrations for schema changes
• Use raw SQL without sanitization (sanitize_sql or parameterized queries only)
• Expose internal IDs in URLs without consideration

Output Templates

When implementing Rails features, provide:

1. Migration file (if schema changes needed)
2. Model file with associations and validations
3. Controller with RESTful actions and strong parameters
4. View files or Hotwire setup
5. Spec files for models and requests
6. Brief explanation of architectural decisions

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