`rails new myapp`	새 앱 생성
`rails new myapp --api`	API 전용 앱 생성
`rails server / rails s`	서버 시작
`rails console / rails c`	콘솔 열기
`rails dbconsole / rails db`	데이터베이스 콘솔
`rails routes`	모든 라우트 표시
`rails routes -g users`	라우트 검색

생성

`rails g model User name:string email:string`	모델 생성
`rails g controller Users index show`	컨트롤러 생성
`rails g scaffold Post title:string body:text`	스캐폴드 생성
`rails g migration AddAgeToUsers age:integer`	마이그레이션 생성
`rails g mailer UserMailer`	메일러 생성
`rails g job ProcessData`	잡 생성
`rails destroy model User`	생성된 파일 삭제

데이터베이스

`rails db:create`	데이터베이스 생성
`rails db:migrate`	마이그레이션 실행
`rails db:rollback`	마이그레이션 롤백
`rails db:seed`	시드 실행
`rails db:reset`	삭제, 생성, 마이그레이션, 시드
`rails db:migrate:status`	마이그레이션 상태

모델

모델 기초

모델 정의

class User < ApplicationRecord
  # Validations
  validates :name, presence: true
  validates :email, uniqueness: true

  # Associations
  has_many :posts
  belongs_to :company
end

유효성 검사

validates :name, presence: true
validates :email, format: { with: URI::MailTo::EMAIL_REGEXP }
validates :age, numericality: { greater_than: 0 }
validates :terms, acceptance: true
validates :password, length: { minimum: 6 }
validates :username, uniqueness: { case_sensitive: false }

콜백

before_validation :normalize_email
before_save :encrypt_password
after_create :send_welcome_email
after_destroy :cleanup_files

스코프

scope :active, -> { where(active: true) }
scope :recent, -> { order(created_at: :desc) }
scope :by_status, ->(status) { where(status: status) }

# Usage: User.active.recent

연관관계

일대다

# User has many Posts
class User < ApplicationRecord
  has_many :posts, dependent: :destroy
end

class Post < ApplicationRecord
  belongs_to :user
end

다대다

# Through join table
class User < ApplicationRecord
  has_many :user_roles
  has_many :roles, through: :user_roles
end

class Role < ApplicationRecord
  has_many :user_roles
  has_many :users, through: :user_roles
end

다형성

class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true
end

class Post < ApplicationRecord
  has_many :comments, as: :commentable
end

쿼리

찾기

User.find(1)
User.find_by(email: "a@b.com")
User.find_by!(email: "a@b.com")  # raises
User.first
User.last
User.all

Where

User.where(active: true)
User.where("age > ?", 18)
User.where(age: 18..30)
User.where.not(role: "admin")
User.where(name: ["Alice", "Bob"])

정렬 및 제한

User.order(:name)
User.order(created_at: :desc)
User.limit(10)
User.offset(20)
User.limit(10).offset(20)

집계

User.count
User.sum(:age)
User.average(:age)
User.maximum(:age)
User.minimum(:age)
User.group(:role).count

조인

User.joins(:posts)
User.includes(:posts)  # eager load
User.left_joins(:posts)

컨트롤러

컨트롤러 기초

RESTful 컨트롤러

class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  def index
    @users = User.all
  end

  def show
  end

  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)
    if @user.save
      redirect_to @user, notice: "Created!"
    else
      render :new
    end
  end

  private

  def set_user
    @user = User.find(params[:id])
  end

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

응답

렌더

render :new
render json: @user
render json: @user, status: :created
render plain: "OK"
render html: "<h1>Hello</h1>".html_safe

리다이렉트

redirect_to users_path
redirect_to @user
redirect_to root_path, notice: "Success"
redirect_back fallback_location: root_path

필터

before_action :authenticate_user!
before_action :set_user, only: [:show, :edit]
after_action :log_activity
around_action :wrap_in_transaction

라우트

라우팅

RESTful 라우트

Rails.application.routes.draw do
  resources :users
  resources :posts, only: [:index, :show]
  resources :comments, except: [:destroy]
end

중첩 라우트

resources :users do
  resources :posts
end
# /users/:user_id/posts/:id

커스텀 라우트

get "/about", to: "pages#about"
post "/login", to: "sessions#create"
match "/auth", to: "auth#callback", via: [:get, :post]

Member & Collection

resources :posts do
  member do
    post :publish
  end
  collection do
    get :search
  end
end

네임스페이스

namespace :admin do
  resources :users
end
# /admin/users

마이그레이션

마이그레이션 예시

테이블 생성

class CreateUsers < ActiveRecord::Migration[7.0]
  def change
    create_table :users do |t|
      t.string :name, null: false
      t.string :email, index: { unique: true }
      t.integer :age
      t.references :company, foreign_key: true
      t.timestamps
    end
  end
end

열 추가

class AddAgeToUsers < ActiveRecord::Migration[7.0]
  def change
    add_column :users, :age, :integer
    add_index :users, :age
  end
end

열 변경

class ChangeNameInUsers < ActiveRecord::Migration[7.0]
  def change
    change_column :users, :name, :string, limit: 100
    rename_column :users, :name, :full_name
  end
end

열 제거

class RemoveAgeFromUsers < ActiveRecord::Migration[7.0]
  def change
    remove_column :users, :age, :integer
  end
end