nested_attr_validation.rb

class Country < ActiveRecord::Base
  validates :name, uniqueness: true
  validates :name, presence: true

  has_many :regions, dependent: :destroy#, inverse_of: :country
  validates_associated :regions
  accepts_nested_attributes_for :regions
end

class Region < ActiveRecord::Base
  validates :name, presence: true
  validates_uniqueness_of :name, scope: :country_id
  
  belongs_to :country
end


# rails console ->
# simple
1. Country.create(name: 'name')
2. Country.first.regions.create(name: 'name') # creates the region
3. Country.first.regions.create(name: 'name') # doesn't create the region (which is what I'd expect)

# with mass assignment
1. c2 = Country.create(name: 'name2')
2. c2.attributes = { regions_attributes: [ { name: 'nn' }, { name: 'nn' } ]}
3. c2.save # creates duplicates. why??

# --------------------------------------------

# test2
c1 = Country.create(name: 'name11')
c1.regions.create(name: 'dd')
r = c1.regions.create(name: 'dd')
pp r.errors
pp c1.regions
pp '------------------------'
data = {
  regions_attributes: [ { name: 'dd' }, { name: 'dd' } ]
}
c2 = Country.create(name: 'name2')
c2.attributes = data
c2.save # creates duplicates. why??
pp c2.errors
pp c2.regions


# test output
#<ActiveModel::Errors:0x00000006c7bf40
 @base=
  #<Region id: nil, name: "dd", country_id: 47, created_at: nil, updated_at: nil>,
 @messages={:name=>["has already been taken"]}>
[#<Region id: 52, name: "dd", country_id: 47, created_at: "2014-07-01 10:54:53", updated_at: "2014-07-01 10:54:53">,
 #<Region id: nil, name: "dd", country_id: 47, created_at: nil, updated_at: nil>]
"------------------------"
#<ActiveModel::Errors:0x00000006eb97a8
 @base=
  #<Country id: 48, name: "name2", created_at: "2014-07-01 10:54:53", updated_at: "2014-07-01 10:54:53">,
 @messages={}>
[#<Region id: 53, name: "dd", country_id: 48, created_at: "2014-07-01 10:54:53", updated_at: "2014-07-01 10:54:53">,
 #<Region id: 54, name: "dd", country_id: 48, created_at: "2014-07-01 10:54:53", updated_at: "2014-07-01 10:54:53">]