Model Associations in Ruby

From the Ruby on Rails cheat sheet · Models & Active Record · verified Jul 2026

Model Associations

Define relationships between models

ruby
class User < ApplicationRecord
  has_many :posts
  has_one :profile
end

class Post < ApplicationRecord
  belongs_to :user
  has_many :comments
end

class Comment < ApplicationRecord
  belongs_to :post
end
✅ belongs_to creates foreign key relationship
💡 dependent: :destroy deletes associated records
🔍 has_many :through for many-to-many relationships
⚡ Use counter_cache to avoid COUNT queries
modelsassociationsrelationships

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