gem 'activerecord_json_validator', '~> 2.0.0'

create_table "users" do |t|
  t.string "name"
  t.json "profile" # First-class JSON with PostgreSQL, yo.
end

class User < ActiveRecord::Base
  # Constants
  PROFILE_JSON_SCHEMA = Rails.root.join('config', 'schemas', 'profile.json')

  # Validations
  validates :name, presence: true
  validates :profile, presence: true, json: { schema: PROFILE_JSON_SCHEMA }
end

user = User.new(name: 'Samuel Garneau', profile: { city: 'Quebec City' })
user.valid? # => false

user = User.new(name: 'Samuel Garneau', profile: { city: 'Quebec City', country: 'Canada' })
user.valid? # => true

user = User.new(name: 'Samuel Garneau', profile: '{invalid JSON":}')
user.valid? # => false
user.profile_invalid_json # => '{invalid JSON":}'

class User < ActiveRecord::Base
  # Constants
  PROFILE_REGULAR_JSON_SCHEMA = Rails.root.join('config', 'schemas', 'profile.json_schema')
  PROFILE_ADMIN_JSON_SCHEMA = Rails.root.join('config', 'schemas', 'profile_admin.json_schema')

  # Validations
  validates :profile, presence: true, json: { schema: lambda { dynamic_profile_schema } } # `schema: :dynamic_profile_schema` would also work

  def dynamic_profile_schema
    admin? ? PROFILE_ADMIN_JSON_SCHEMA : PROFILE_REGULAR_JSON_SCHEMA
  end
end

class User < ActiveRecord::Base
  # Constants
  JSON_SCHEMA = Rails.root.join('config', 'schemas', 'profile.json_schema')
  # JSON_SCHEMA = { 'type' => 'object', 'properties' => { 'foo' => { 'type' => 'integer', 'minimum' => 3 } } }
  # JSON_SCHEMA = '{"type":"object","properties":{"foo":{"type":"integer","minimum":3}}}'

  # Validations
  validates :profile, presence: true, json: { schema: JSON_SCHEMA }
end

class User < ActiveRecord::Base
  # Validations
  validates :profile, presence: true, json: { message: ->(errors) { errors }, schema: 'foo.json_schema' }
end

user = User.new.tap(&:valid?)
user.errors.full_messages
# => [
#      'The property '#/email' of type Fixnum did not match the following type: string in schema 2d44293f-cd9d-5dca-8a6a-fb9db1de722b#',
#      'The property '#/full_name' of type Fixnum did not match the following type: string in schema 2d44293f-cd9d-5dca-8a6a-fb9db1de722b#',
#    ]