Rails ActiveRecord 参考

ActiveRecord 完整参考：迁移、关联、验证、回调、命名作用域和查询接口模式。

1. 迁移

class CreateArticles < ActiveRecord::Migration[7.1]
  def change
    create_table :articles do |t|
      t.string   :title,    null: false, limit: 300
      t.string   :slug,     null: false, index: { unique: true }
      t.text     :content,  null: false
      t.string   :status,   null: false, default: "draft"
      t.jsonb    :metadata, default: {}
      t.references :author, null: false, foreign_key: { to_table: :users }
      t.timestamps
    end
  end
end

2. 关联

class User < ApplicationRecord
  has_many :articles, foreign_key: :author_id, dependent: :nullify
  has_one  :profile, dependent: :destroy
end

class Article < ApplicationRecord
  belongs_to :author, class_name: "User"
  has_many   :comments, dependent: :destroy
  has_and_belongs_to_many :tags
end

3. 验证

class Article < ApplicationRecord
  validates :title,  presence: true, length: { minimum: 5, maximum: 300 }
  validates :slug,   presence: true, uniqueness: true
  validates :status, inclusion: { in: %w[draft published archived] }
  validates :published_at, presence: true, if: :published?

  validate :slug_not_reserved
  private
  def slug_not_reserved
    errors.add(:slug, "是保留字") if %w[admin api].include?(slug)
  end
end

4. 作用域与查询

class Article < ApplicationRecord
  scope :published, -> { where(status: "published") }
  scope :recent,    -> { order(created_at: :desc) }
  scope :search,    ->(q) { where("title ILIKE ?", "%#{q}%") }
end

articles = Article.published.recent.page(1).per(20)
Article.includes(:author, :tags).where(tags: { name: "ruby" })

Rails ActiveRecord 参考

1. 迁移

2. 关联

3. 验证

4. 作用域与查询

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