ruby-on-rails - 验证 has_and_belongs_to_many 的存在

Question

嗨，我在模型中使用 has_and_belongs_to_many。
我想为种类设置存在的 valitor。
并将每个核心的最大种类数设置为 3

class Core < ActiveRecord::Base
  has_and_belongs_to_many :kinds, :foreign_key => 'core_id', :association_foreign_key => 'kind_id'
end

我能怎么做？

谢谢

Answer 1

validate :require_at_least_one_kind
validate :limit_to_three_kinds

private

def require_at_least_one_kind
  if kinds.count == 0
    errors.add_to_base "Please select at least one kind"
  end
end

def limit_to_three_kinds
  if kinds.count > 3
    errors.add_to_base "No more than 3 kinds, please"
  end
end