fetch_by_name

fetch_by_name.rb

# -*- encoding : utf-8 -*-
module FetchByName
  def fetch_by_name(name, field_name = :name)
    if id = Rails.cache.read("cached_#{self.name}_#{field_name}_#{name}")
      self.find(id)
    else
      record = self.where(field_name => name).first || raise(ActiveRecord::RecordNotFound)
      record.tap{|record| Rails.cache.write("cached_#{self.name}_#{field_name}_#{name}", record.id)}
    end
  end
end

class User < ActiveRecord::Base
  extend FetchByName
end

class Tag < ActiveRecord::Base
  extend FetchByName
end

[3] pry(main)> User.fetch_by_name("hooopo")
  User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`name` = 'hooopo' LIMIT 1 #第一次正常的SQL
[4] pry(main)> User.fetch_by_name("hooopo")
  User Load (0.2ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1 # 第二次会用主键查询
[5] pry(main)> User.fetch_by_name("hooopo") # 由于用了https://github.com/csdn-dev/second_level_cache，第二次以后不会去读数据库