验证rails 3.2中创建的has_many对象的计数

Question

验证rails 3.2中创建的has_many对象的数量？

我需要对关联对象的"最大/最小"计数进行自定义验证.我有房地产,有

has_many :realty_images, :dependent => :destroy
accepts_nested_attributes_for :realty_images

和realty_image:

class RealtyImage < ActiveRecord::Base
  attr_accessible :avatar, :image, :realty_id
  belongs_to :realty

  #here a suppose I need to put some kind of custom validation
  mount_uploader :image, ImageUploader
end

Answer 1

标准验证方法适用于关联:

class Ad
  has_many :realty_images

  # make sure there are some images
  validates_presence_of :realty_images

  # or make sure the number of images is in certain range
  validates_length_of :realty_images, within: 5..10
end

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