如何在保存新记录之前检查数据库状态

Question

是否有一种更为红宝石的惯用方法来处理检查数据库是否有5条记录,然后使用if语句,是否应该在过滤器或任何类型的验证中完成？

saved_count = Model.where(is_active: true).count
if saved_count == MAX_SAVED
  return {error: 'Cannot save more than 5 records'}
end

Answer 1

只需使用验证:

class Model
  # I would create a scope to use it in validation
  # scope :active, -> { where(is_active: true) }

  validate :max_count

  private

  def max_count
    errors.add(:base, 'Cannot save more than 5 records') if self.class.active.count == 5
  end
end