ruby - NameError:未初始化的常量 Song ...Programming Ruby

Question

试图通过这个编程 ruby​​ 站点获取 ruby​​，但我被这个语法困住了

class SongList


  def initialize
    @songs = Array.new
  end

  def append(aSong)
    @songs.push(aSong)
    self
  end


  def deleteFirst
    @songs.shift
  end
  def deleteLast
    @songs.pop
  end


end

当我去添加一首歌时...

list = SongList.new
list.append(Song.new('title1', 'artist1', 1))

我收到此错误消息:

NameError: uninitialized constant Song ...Programming Ruby 

我看到我需要 require 变量 Song，但我不确定在 SongList 类中的什么地方做它....

Answer 1

您可以使用 ruby Struct类:

A Struct is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.

class SongList
  def initialize
    @songs = [] # use [] instead of Array.new
  end

  def append(aSong)
    @songs.push(aSong)
    self
  end

  def delete_first
    @songs.shift
  end
  def delete_last
    @songs.pop
  end
end

Song = Struct.new(:song_name, :singer, :var)

list = SongList.new
list.append(Song.new('title1', 'artist1', 1))
# => #<SongList:0x9763870
#     @songs=[#<struct Song song_name="title1", singer="artist1", var=1>]> var=1>]>