如何在保存新记录之前检查数据库状态 [英] How to check for a database state before saving new records

问题描述

是否有更 ruby​​ 惯用的方法来处理检查数据库是否有 5 条记录，而不是使用 if 语句，这应该在过滤器或任何类型的验证中完成吗?

Is there a more ruby idiomatic way to handle checking if database has 5 records other then to use an if statement, should this be done in a filter or any type of validation?

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

推荐答案

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

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