vkill'blog

  def authenticate(userid, passwd)
    begin
      u = User.find(:first, :conditions=>["name = ? and passwd = ?", userid, passwd])
      raise "is_admin miss" if !u.is_admin
      #@userid, @is_valid_users, @is_admin_users = (u and u.id ? [u.name,u.is_valid,u.is_admin] : [nil,false,false])
    rescue
      @err = $!
    else
      @err = nil
    end
  end

#先建个抽象model类，因为要所有find生效，所以建个抽象类，相当于中间类
>ruby script\generate model abstract_model

#编辑 app\models\abstract_model.rb 内容如下
class AbstractModel < ActiveRecord::Base
  self.abstract_class = true  #这个很重要，详见 http://blog.vkill.net/read.php/161.htm
  #这个方法是扩展find，加上异常处理
  def self.find(*args)
    begin
      super
    rescue => err
      @errors = err.message
    end
  end
  #这个方法是查询错误
  def self.errors_full_message()
    @errors || nil
  end
end

#修改User类为抽象类的子类，编辑 app\models\user.rb 内容如下
class User < AbstractModel
end

#如何使用呢？还是最开始的那个helper例子，现在变的很简单了吧，呵呵
  def authenticate(userid, passwd)
    u = User.find(:first, :conditions=>["name = ? and passwd = ?", userid, passwd])
    if err = User.errors_full_message
      @err_auth = err
    else
      if u
        begin
          @userid, @is_valid_users, @is_admin_users = (u and u.id ? [u.name,u.is_valid,u.is_admin] : [nil,false,false])
        rescue =>err
          @err_auth = err.message
        else
          @err_auth = nil
        end
      else
        @err_auth = 'auth error, userid or passwd error'
      end
    end
  end