rails-way

Rails Way Patterns

Core Principles

• Convention over Configuration — follow Rails conventions
• DRY — don't repeat yourself
• Thin controllers, fat models — business logic in models/concerns

Controller Rules

• HTTP flow only: receive request, call model, render response
• No business logic, no conditionals, no calculations
• Always use strong parameters
• Query through parent associations

# Good — thin controller
class Admin::UsersController < Admin::ApplicationController
  def create
    @user = current_admin.users.build(user_params)
    if @user.save
      redirect_to [:admin, @user], notice: t('.success')
    else
      render :new, status: :unprocessable_entity
    end
  end

  private

  def user_params
    params.require(:user).permit(:name, :email)
  end
end

Model Rules

• Validations for data integrity
• Callbacks for lifecycle events
• Scopes for chainable queries
• Business logic only — display/presentation logic belongs in helpers
• class << self for class methods (NOT def self.)
• Enum predicate methods: task.pending? (NOT task.status == "pending")
• Enum scopes: Task.status_pending (NOT Task.where(status: :pending))

class Task < ApplicationRecord
  include Task::StatusTransitions
  include AttributeLabels

  acts_as_paranoid

  belongs_to :user
  validates :title, presence: true
  enum :status, { pending: 0, in_progress: 1, completed: 2 }

  scope :due_soon, -> { where(due_at: ..3.days.from_now) }

  class << self
    def find_by_code(code)
      find_by(code: code)
    end
  end
end

Display Logic → Helpers (NOT Models)

# BAD — display logic in model
class User < ApplicationRecord
  def full_name_with_role
    "#{name} (#{role.humanize})"
  end

  def status_color
    active? ? "green" : "red"
  end
end

# GOOD — display logic in helper
module UsersHelper
  def user_full_name_with_role(user)
    "#{user.name} (#{user.role.humanize})"
  end

  def user_status_color(user)
    user.active? ? "green" : "red"
  end
end

No Service Classes

# BAD — service class
class TaskService
  def advance(task); end
end

# GOOD — model concern
module Task::StatusTransitions
  extend ActiveSupport::Concern

  def advance!
    case status
    when "pending" then update!(status: :in_progress)
    when "in_progress" then update!(status: :completed)
    end
  end
end

Forms

• Use Rails form helpers (NOT raw HTML <form>, <input>)
• Use form.submit for double-click prevention (NOT <button type="submit">)
• Use URL helpers (NOT hardcoded strings)

Error Handling

• Do NOT rescue errors — Sentry handles them
• Exception: rescue expected errors with clear comments

Credentials

• Rails.application.credentials.dig(:section, :key) (NOT ENV['KEY'])

Pagination

• Model.page(params[:page]).per(25) (Kaminari)

Soft Deletes

• record.destroy = soft delete (Paranoia)
• record.really_destroy! = permanent delete

Reference Models

• Use ActiveHash for read-only static data
• belongs_to_active_hash :country