#2 Dynamic find_by Methods

Mar 06, 2007 | 1 minute | Active Record

Shorten simple finds considerably and improve readability by using the dynamic find_all_by and find_by methods.

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下面给大家演示一个在Rails中更加优雅地使用find方法进行数据查询的方式。例子中Task类有一个属性complete表明任务是否已经完成（complete字段是false意味着未完成），incomplete和last_incomplete方法分别用来返回所有未完成的和最后一个未完成的任务。

          ruby
        
class TaskController < ApplicationController
  def incomplete
    @tasks = Task.find(:all, :conditions => ['complete = ?', false])
  end

  def last_incomplete 
    @task = Task.find(:first, :conditions => ['complete =?', false], :order => 'created_at DESC')
  end
end

更好的方式是将这句代码

          ruby
        
@tasks = Task.find(:all, :conditions => ['complete = ?', false])

用这句来替换

          ruby
        
@tasks = Task.find_all_by_complete(false)

如果想查找某一个Task，使用find_by。比如,查找最后一个未完成的任务将last_incomplete方法中的这句代码

          ruby
        
@task = Task.find(:first, :conditions => ['complete =?', false], :order => 'created_at DESC')

改为

          ruby
        
@task = Task.find_by_complete(false, :order => 'created_at DESC')

find_by方法可以像find方法样接受order参数。