如何访问哈希值数组中的第一项

Question

我有一个哈希值，它的值是歌词数组（第 1 行、第 2 行等）

代码：

class Song
    def initialize(lyrics)
       @lyrics = lyrics 
    end
    def get_song_name()
        puts @lyrics.keys
    end
    def get_first_line()
        puts @lyrics.values[0]
    end
end

wasted = Song.new({"Wasted" => ["I like us better when we're wasted",
    "It makes it easier to see"]})

real_world = Song.new("Real World" => ["Straight up what do you want to learn about here", "if i was someone else would this all fall apart"])

wasted.get_song_name()
wasted.get_first_line()
#=>I like us better when we're wasted
#=>It makes it easuer to see

所以当我调用wasted.get_first_line 时，我希望它获取值数组中的第一项。我试过@lyrics.values[0]，但它返回歌曲的两行而不是第一行。

我该如何做到这一点？

Answer 1

你需要明白，在上面的代码中@lyrics是一个Hash。以下是您正在做的事情以及它的含义：

@lyrics
# => {"Wasted"=>["I like us better when we're wasted", "It makes it easier to see"]} 


@lyrics.values
# => [["I like us better when we're wasted", "It makes it easier to see"]] 

@lyrics.values[0]
# => ["I like us better when we're wasted", "It makes it easier to see"] 

@lyrics.values[0][0]

# => "I like us better when we're wasted" 

因此，要访问第一行，您需要获取 values 数组的第一个元素。即

@lyrics.values[0][0]

或

@lyrics.values.first.first

Answer 2

让我们以这个哈希为例：

x = {foo: [:bar, :baz]}

x.values             # => [[:bar, :baz]]
x.values.first       # => [:bar, :baz]
x.values.first.first # => :bar

换句话说，@lyrics.values[0] 将返回 @lyrics 哈希中的第一个值，这是两首歌曲的数组。您仍然必须从该数组中取出第一首歌曲。

Answer 3

这不是原始问题的答案，但如果我是你，我会像下面这样修改课程。它将更倾向于将歌曲名称和歌词行存储为单独的属性，而不是将它们合并为哈希 - 这违背了拥有 Song 类的全部目的。

class Song
    attr_accessor :song_name, :lyrics

    def initialize(song_name, lyrics)
       @song_name = song_name
       @lyrics = lyrics 
    end
end

请注意，您可能不需要get_first_line 方法。你总是可以使用Array#first 来达到同样的效果：

real_world = Song.new("Real World", ["Line 1", "Line 2"])
puts real_world.lyrics.first # Prints "Line 1"

您还可以使用数组索引访问歌词行

puts real_world.lyrics[1] # Prints "Line 2"