Rails 100% newb 问题 - send() 方法 [英] Rails 100% newb issue - send() method

问题描述

有人可以帮我理解下面列出的send()"方法的用途吗?下面的代码，当我阅读它时，它的用途是没有意义的.

这是一个使用 Ruby 1.8.7 和 Rails 1.2.3 的 Rails 应用程序.升级的事情请不要骂我，这是客户的环境，我没有那种闲暇.

不过不用说，我所指的语句是这样的；

def do_schedule@performance = Performance.new(params[:performance])@performer = Performer.find(params[:performer_id])selected_track = params[:selected_track]如果 FileTest.exists?(File.expand_path(@performer.photo))@performance.photo = File.open(File.expand_path(@performer.photo))结尾@performance.audio = File.open(File.expand_path(@performer.send(selected_track)))如果@performance.saveflash[:notice] = '已安排表演者.'重定向到:控制器 =>:表演者，:动作=>:指数别的渲染:动作=>'日程'结尾结尾

<块引用>

表演模特

class Performer /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/ivalidates_confirmation_of :emailvalidates_presence_of :audio_one, :audio_two, :audio_three, :photo, :if =>:提交after_create :salt_access_key序列化:可用性序列化:阶段attr_accessor :other_type_of_musicbefore_save :set_other_typedef set_other_type如果 type_of_music == '其他'self.type_of_music = "Other - #{other_type_of_music}" 除非 other_type_of_music.blank?结尾结尾def salt_access_keyupdate_attribute(:access_key, Digest::SHA1.hexdigest("--#{self.id}--#{self.name}--#{self.festival.year}"))结尾def preferred_stages阶段 = []节日 = Festival.find(self.festival_id.to_i)self.stages.collect { |键，值 |id = key.gsub(/[\D]/, '').to_i如果 id >0阶段<

包含它的控制器是性能.我一直在搜索 Google，试图弄清楚 '@performer.send(selected_track)' 的实际目的是什么，但感觉就像在漩涡中划船.

有人可以帮助我更好地理解这一点吗?

谢谢.

解决方案

send 方法的 Ruby 实现，用于向对象发送方法消息，其工作方式如下:

class Car定义开始把vroom"结尾私人的def engine_temp把恰到好处"结尾结尾@car = [e-mail] # 输出:[e-mail](:start) # 输出:vroom

这是基础知识，另外一条重要信息是 send 将允许您将消息发送到 PRIVATE 方法，而不仅仅是公共方法.

@car.engine_temp # 这个不行，会抛出异常@car.send(:engine_temp) # 输出:恰到好处

至于您的特定发送调用将执行的操作，Performer 类中很可能有一个 def method_missing 用于捕获该调用并执行某些操作.

希望这会有所帮助，祝你好运！

Could someone please help me to understand what the 'send()' method listed below is used for? The code below, when I am reading it, makes no sense what purpose it's serving.

It's a Rails app using Ruby 1.8.7 with Rails 1.2.3. Please don't harp on me about upgrading, it's a client's environment, so I don't have that sort of leisure.

Needless to say though, the statement I am referring to is like this;

def do_schedule
  @performance = Performance.new(params[:performance])
  @performer = Performer.find(params[:performer_id])
  selected_track = params[:selected_track]
  if FileTest.exists?(File.expand_path(@performer.photo))
    @performance.photo = File.open(File.expand_path(@performer.photo))
  end

  @performance.audio = File.open(File.expand_path(@performer.send(selected_track)))

  if @performance.save
    flash[:notice] = 'Performer scheduled.'
    redirect_to :controller => :performer, :action => :index
  else
    render :action => 'schedule'
  end
end

Performer Model

class Performer < ActiveRecord::Base
  file_column :audio_one
  file_column :audio_two
  file_column :audio_three
  file_column :photo

  belongs_to :festival
  validates_presence_of :name, :first_name, :last_name, :address, :city, :state, :zip, :daytime_phone, :availability, :stages
  validates_format_of :email, :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i
  validates_confirmation_of :email

  validates_presence_of :audio_one, :audio_two, :audio_three, :photo, :if => :submitted

  after_create :salt_access_key
  serialize :availability
  serialize :stages

  attr_accessor :other_type_of_music
  before_save :set_other_type

  def set_other_type
    if type_of_music == 'Other'
      self.type_of_music = "Other - #{other_type_of_music}" unless other_type_of_music.blank?
    end
  end

  def salt_access_key
    update_attribute(:access_key, Digest::SHA1.hexdigest("--#{self.id}--#{self.name}--#{self.festival.year}"))
  end

  def preferred_stages
    stages = []
    festival = Festival.find(self.festival_id.to_i)
    self.stages.collect { | key, value |
      id = key.gsub(/[\D]/, '').to_i
      if id > 0
        stages << festival.performance_stages.find(id).name
      end
    }
    return stages
  end
end

The controller that this is contained in is Performance. I have been scouring Google trying to figure out what purpose that '@performer.send(selected_track)' is actually doing, but feel like I'm rowing against a whirlpool.

Can someone please help me make better sense out of this?

Thanks.

解决方案

The Ruby implementation for the send method, which is used to send a method message to an object, works like this:

class Car

  def start
    puts "vroom"
  end

  private

  def engine_temp
    puts "Just Right"
  end

end

@car = Car.new
@car.start # output: vroom
@car.send(:start) # output: vroom

That's the basics, an additional piece of important information is that send will allow you you send in messages to PRIVATE methods, not just public ones.

@car.engine_temp  # This doesn't work, it will raise an exception
@car.send(:engine_temp)  # output: Just Right

As for what your specific send call will do, more than likely there is a def method_missing in the Performer class that is setup to catch that and perform some action.

Hope this helps, good luck!

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