一次只允许 ActiveRecord 模型中的多个属性之一出现答案

【问题标题】：Allow only one of multiple attributes in an ActiveRecord model to be present at a time一次只允许 ActiveRecord 模型中的多个属性之一出现
【发布时间】：2016-03-13 01:34:44
【问题描述】：

我正在努力做到这一点，以便在任何给定时间只能填充三列中的一列。

这是我想到的一些伪代码：

class Model < ActiveRecord::Base
  validates :column_one, presence: true,
    absence: true if (:column_two.present? || :column_three.present?)
  validates :column_two, presence: true,
    absence: true if (:column_one.present? || :column_three.present?)
  validates :column_three, presence: true,
    absence: true if (:column_one.present? || :column_two.present?)
end

是否可以在模型级别执行此操作，还是我必须在控制器或参数中进行管理？

【问题讨论】：

标签： ruby-on-rails ruby ruby-on-rails-4 rails-activerecord

【解决方案1】：

您可以使用带有unless 的过程：

validates :column_one, presence: true, unless: Proc.new { |r|
  r.column_two.present? || r.column_two.present?
}
validates :column_two, presence: true, unless: Proc.new { |r|
  r.column_one.present? || r.column_three.present?
}
validates :column_three, presence: true, unless: Proc.new { |r|
  r.column_one.present? || r.column_two.present?
}

或命名函数的符号：

validates :column_one, presence: true, unless: :other_columns_present

private

def other_columns_present
  # do checks here
end

【讨论】：

【解决方案2】：

要在单个验证中进行检查而不重复代码，请使用自定义验证方法：

class Model < ActiveRecord::Base
  validate :there_can_be_only_one
end

def there_can_be_only_one
  if [column_one, column_two, column_three].count(&:present?) > 1
    column_with_error = column_one.present? ? :column_one : :column_two
    errors.add(column_with_error,
      "can't be present if any other column in [column_one, column_two, column_three] is also present"
  end
end

【讨论】：