Ruby學習系列----疑問(2)

class Song
	def initialize(name,artist,duration)
		@name = name
		@artist = artist
		@duration = duration
		
	end
	def to_s
		"Song : #{@name}--#{@artist}  (#{@duration})"
	end
end
class SongList
	def initialize
		@songs = Array.new
	end
	def append(aSong)
		@songs.push(aSong)
		self
	end
	def show=(index)
		#puts "show #{index}"
		#puts "@songs.length : #{@songs.length}"
		#puts "@songs[#{index}] : #{@songs[index]}"
		@songs[index]
	end
	def show(index)
		@songs[index]
	end
	def [](key)
		if key.kind_of?(Integer)
			@songs[key]
		else
			
		end
	end
	def size
		@songs.length
	end
end


list = SongList.new
list.
	append(Song.new('title1','artist1',1)).
	append(Song.new('title2','artist2',2)).
	append(Song.new('title3','artist3',3)).
	append(Song.new('title4','artist4',4))
#puts(list.show = 1)
p list.show = 2  >> 2
p list.show(2)   >>#<Song:0x2b36d28 @duration=3, @artist="artist3", @name="title3">
p list[2]        >>#<Song:0x2b36d28 @duration=3, @artist="artist3", @name="title3">

疑问:

   为什么调用 list.show = 2 返回的是2 ?
    不是应该和list.show(2)一样 返回的是@Songs[2]的 Song实例 吗?