Rails: why is calling `valid?` only validate some of associated record not all associated records

Question

I have a model Order which is like

# app/models/order.rb
class Order< ApplicationRecord
   has_one :detail
   has_one :extra
..
end

I have two orders

order1 = Order.first
order1.detail #<OrderDetail:0x00 name: "abc", remark: 'test1'>
order1.extra  #<OrderExtra:0x00 email: nil, recipent: nil>

order2 = Order.second
order1.detail #<OrderDetail:0x00 name: "abc", remark: 'test1'>
order1.extra  #<OrderExtra:0x00 email: nil, recipent: "xyz">

When I call order1.valid? or order1.save! it will not check OrderExtra validation and returns true. But when I call order2.valid? or order2.save! it checks OrderExtra validation.

order1.save! # true
order2.save! # ActiveRecord Invalid OrderExtra

I want to know how rails checks if they want to check associated validation when call save! and the reason behind that.

Please let me know if any additional requirement needed on this.

Answer 1

use the validates_associated for enforcing associated model validations

class Book < ActiveRecord::Base
  has_many :pages
  belongs_to :library

  validates_associated :pages, :library
end

This validation will not fail if the association hasn't been assigned. If you want to ensure that the association is both present and guaranteed to be valid, you also need to use validates_presence_of .

class Library < ActiveRecord::Base
 has_many :books
 validates_presence_of :name
end