ruby-on-rails - rails ，ActiveRecord : Callback run during #reload

Question

我有一个模型，其属性是从持久列值的值生成的。

class Result < ActiveRecord::Base
  belongs_to :job
  belongs_to :customer
  has_many :records, through: :job

  def processed_records
    @processed_records ||=
      begin
        status_flagged + status_invalid +
          status_unknown + status_valid
      end
  end
end

我的问题是 Result 对象有时必须调用 #reload 才能从数据库中获取新值。有没有我可以 Hook 的回调来清除 @processed_records 的值，以便下一次调用将重新计算该值？

换句话说，我希望它能工作:

RSpec.describe Result, :type => :model do
  subject { create(:result) }

  it 'should update #processed_records on reload' do
    initial_value = subject.processed_records

    other_instance = Result.find(subject.id)
    other_instance.increment(:status_flagged)
    other_instance.save

    subject.reload
    expect(subject.processed_records).to eq(initial_value + 1)
  end
end

Answer 1

您可以覆盖模型中的 reload 方法:

def reload
  super

  # code with whatever you need to clean, for example:
  @processed_records = nil
end