Rails 嵌套属性：需要至少两条记录

Question

如何才能使提交产品时至少需要两条选项记录？

class Product < ActiveRecord::Base
  belongs_to :user
  has_many :options, :dependent => :destroy
  accepts_nested_attributes_for :options, :allow_destroy => :true, :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }
  validates_presence_of :user_id, :created_at
  validates :description, :presence => true, :length => {:minimum => 0, :maximum => 500}
end

class Option < ActiveRecord::Base
  belongs_to :product
  validates :name, :length => {:minimum => 0, :maximum => 60}                  
end

Answer 1

class Product < ActiveRecord::Base
  #... all your other stuff
  validate :require_two_options

  private
    def require_two_options
      errors.add(:base, "You must provide at least two options") if options.size < 2
    end
end

Answer 2

只是考虑一下 karmajunkie 答案：我会使用 size 而不是 count 因为如果某些构建（且未保存）的嵌套对象有错误，则不会考虑它（它不是尚未在数据库上）。

class Product < ActiveRecord::Base
  #... all your other stuff
  validate :require_two_options

  private
    def require_two_options
      errors.add(:base, "You must provide at least two options") if options.size < 2
    end
end

Answer 3

如果您的表单允许删除记录，则 .size 将不起作用，因为它包含标记为销毁的记录。

我的解决方案是：

validate :require_two_options

private
 def require_two_options
    i = 0
    product_options.each do |option|
      i += 1 unless option.marked_for_destruction?
    end
    errors.add(:base, "You must provide at least two option") if i < 2
 end

Answer 4

更整洁的代码，用 Rails 5 测试：

class Product < ActiveRecord::Base
  OPTIONS_SIZE_MIN = 2
  validate :require_two_options

  private

  def options_count_valid?
    options.reject(&:marked_for_destruction?).size >= OPTIONS_SIZE_MIN
  end

  def require_two_options
    errors.add(:base, 'You must provide at least two options') unless options_count_valid?
  end
end

Answer 5

我想知道为什么没有人提到这个简单的解决方案。只需将其添加到您的父类中：

class Product < ActiveRecord::Base

  ...
  
  validates :options, :length => { :minimum => 2 }

end

在 Rails 5.2.8（也可能更高版本）中对我来说就像一个魅力。