音乐脚本解决方案

Question

伙计们

我是ruby的初学者，在我的实践中，我想到了一个音乐脚本，有一点让我昏昏欲睡:当我在​​中输入Scale.major_by_note ('C')的时候，一切都很好，但是如果我输入Scale.major_by_note ('C #')，它就不能工作，为了让它工作，我必须放一个"C #/ Db"，帮助我确保"C“和"C #”和"C #/ Db"，谢谢！以下是脚本：

class Scale
  NATURAL = %w[C D E F G A B].freeze
  ACCIDENT = %w[C# Db D# Eb F# Gb G# Ab A# Bb].freeze
  CHROMATIC = %w[C C#/Db D D#/Eb E F F#/Gb G G# A A#/Bb B].freeze
  SCALE_MAJOR_PATTERN = [0, 2, 4, 5, 7, 9, 11, 12].freeze # T T st T T T st
  SCALE_MINOR_PATTERN = [0, 2, 3, 5, 7, 8, 10, 12].freeze # T st T T st T T

  def self.show_all_scales(note)
    major = Scale.major_by_note(note)
    minor = Scale.minor_by_note(note)
    all = { major: major, minor: minor}
    
  end

  def self.major_by_note(note)
    major_note_index = CHROMATIC.index(note)

    SCALE_MAJOR_PATTERN.map do |major_interval| # Interação
      major_scale_note_index = major_note_index + major_interval

      if major_scale_note_index <= (CHROMATIC.length - 1)
        CHROMATIC[major_scale_note_index]

      else
        reseted_major_scale_note_index = major_scale_note_index - CHROMATIC.length
        CHROMATIC[reseted_major_scale_note_index]
      end
    end
  end

  def self.minor_by_note(note)
    minor_note_index = CHROMATIC.index(note)

    SCALE_MINOR_PATTERN.map do |minor_interval|
      minor_scale_note_index = minor_note_index + minor_interval

      if minor_scale_note_index <= (CHROMATIC.length - 1)
        CHROMATIC[minor_scale_note_index]
      else
        reseted_minor_scale_note_index = minor_scale_note_index - CHROMATIC.length
        CHROMATIC[reseted_minor_scale_note_index]
      end
    end
  end
end```

Answer 1

当你输入的时候

%w[C C#/Db D D#/Eb E F F#/Gb G G# A A#/Bb B]

Ruby正在将其转换为字符串数组：

["C", "C#/Db", "D", "D#/Eb", "E", "F", "F#/Gb", "G", "G#", "A", "A#/Bb", "B"]

虽然你知道C#和Db是同一个音符，但Ruby并非如此，它认为本例中的音符叫做C#/Db。当它试图查找CHROMATIC.index("C#")时，它返回的是nil，因为数组中没有C#。

一种解决方案可能是这样编写它：

  CHROMATIC = %w[C C# D D# E F F# G G# A A# B].freeze
  CHROMATIC_PAIR_MAP = {
    "Db" => "C#",
    "Eb" => "D#",
    "Gb" => "F#",
    "Ab" => "B#",
  }

  ...

  def self.index_of_note(note)
    CHROMATIC.index(note) ||
      CHROMATIC.index(CHROMATIC_PAIR_MAP[note])
  end

  def self.major_by_note(note)
    major_note_index = index_of_note(note)

在这里，我创建了一个新的辅助方法来获取注释的索引，方法是直接从CHROMATIC数组中获取索引，或者在CHROMATIC_PAR_MAP散列中查找note键。只有当CHROMATIC.index(note)返回nil时，它才会在哈希表中执行查找。这是我在控制台(Irb)中得到的：

irb(main):191:0> Scale.major_by_note("C#")
=> ["C#", "D#", "F", "F#", "G#", "A#", "C", "C#"]
irb(main):192:0> Scale.major_by_note("Db")
=> ["C#", "D#", "F", "F#", "G#", "A#", "C", "C#"]
irb(main):193:0> Scale.major_by_note("D#")=> ["D#", "F", "G", "G#", "A#", "C", "D", "D#"]
irb(main):194:0> Scale.major_by_note("Eb")=> ["D#", "F", "G", "G#", "A#", "C", "D", "D#"]

完整的新类：

class Scale
  NATURAL = %w[C D E F G A B].freeze
  ACCIDENT = %w[C# Db D# Eb F# Gb G# Ab A# Bb].freeze
  CHROMATIC = %w[C C# D D# E F F# G G# A A# B].freeze
  SCALE_MAJOR_PATTERN = [0, 2, 4, 5, 7, 9, 11, 12].freeze # T T st T T T st
  SCALE_MINOR_PATTERN = [0, 2, 3, 5, 7, 8, 10, 12].freeze # T st T T st T T

  CHROMATIC_PAIR_MAP = {
    "Db" => "C#",
    "Eb" => "D#",
    "Gb" => "F#",
    "Ab" => "B#",
  }

  def self.show_all_scales(note)
    major = Scale.major_by_note(note)
    minor = Scale.minor_by_note(note)
    all = { major: major, minor: minor}
  end

  def self.major_by_note(note)
    major_note_index = index_of_note(note)
    SCALE_MAJOR_PATTERN.map do |major_interval| # Interação
      major_scale_note_index = major_note_index + major_interval

      if major_scale_note_index <= (CHROMATIC.length - 1)
        CHROMATIC[major_scale_note_index]

      else
        reseted_major_scale_note_index = major_scale_note_index - CHROMATIC.length
        CHROMATIC[reseted_major_scale_note_index]
      end
    end
  end

  def self.minor_by_note(note)
    minor_note_index = CHROMATIC.index(note)

    SCALE_MINOR_PATTERN.map do |minor_interval|
      minor_scale_note_index = minor_note_index + minor_interval

      if minor_scale_note_index <= (CHROMATIC.length - 1)
        CHROMATIC[minor_scale_note_index]
      else
        reseted_minor_scale_note_index = minor_scale_note_index - CHROMATIC.length
        CHROMATIC[reseted_minor_scale_note_index]
      end
    end
  end

  def self.index_of_note(note)
    CHROMATIC.index(note) ||
      CHROMATIC.index(CHROMATIC_PAIR_MAP[note])
  end
end