3

想象一下下面的代码：

class SimpleLetter
  def values
    ("a" .. "z").to_a
  end

  def ===(other)
    values.include?(other)
  end
end

class Vowel < SimpleLetter
  def values
    ["a","e","i","o","u"]
  end
end

class Consonant < SimpleLetter
  def values
    super - Vowel.new.values
  end
end

objects = ("a" .. "f").to_a + (1 .. 5).to_a

objects.each do |letter|
  case letter
    when Vowel.new
      puts "#{letter} it's a vowel"
    when Consonant.new
      puts "#{letter} it's a consonant"
    else
      puts "#{letter} it's something else"
  end
end

我本可以选择任何其他类，我只是以它们为例。我非常喜欢 Scalamatch和提取器，我认为这可能是在 Ruby 中编写相同内容的好方法。有没有更好的方法来编写上述内容而不必实例化新对象以便我可以调用他们的===方法？

只是为了避免不必要的帖子，是的，我知道我可以这样做：

case letter
  when ["a","e","i","o","u"].include?(letter)
    # ...
end
4

5 回答 5

5

你不需要角色的类。将它们设置为数组，并在 case 语句中使用 splat 运算符。

SimpleLetter = ("a" .. "z").to_a
Vowel        = %w[a e i o u]
Consonant    = SimpleLetter - Vowel

(("a" .. "f").to_a + (1 .. 5).to_a).each do |letter|
  case letter
    when *Vowel
      puts "#{letter} it's a vowel"
    when *Consonant
      puts "#{letter} it's a consonant"
    else
      puts "#{letter} it's something else"
  end
end
于 2011-05-23T20:04:01.223 回答
4

===也适用于块：

Letters = ('a'..'z').to_a
Vowels = ['a','e','i','o','u']
Consonants = Letters - Vowels

Vowel = lambda { |x| Vowels.include? x }
Consonant = lambda { |x| Consonants.include? x }

objects = ("a" .. "f").to_a + (1 .. 5).to_a

objects.each do |object|
  case object
    when Vowel
      puts "#{object} is a vowel."
    when Consonant
      puts "#{object} is a consonant."
    else
      puts "#{object} is an object."
  end
end
于 2011-05-23T20:09:16.683 回答
3

您可以使用类方法而不是实例方法：

class SimpleLetter
    def self.values
        ("a" .. "z").to_a
    end 

    def self.===(other)
        values.include?(other)
    end 
end

class Vowel < SimpleLetter
    def self.values
        ["a","e","i","o","u"]
    end 
end

class Consonant < SimpleLetter
    def self.values
        super - Vowel.values
    end 
end

objects = ("a" .. "f").to_a + (1 .. 5).to_a

objects.each do |letter|

    case letter
        when Vowel
            puts "#{letter} it's a vowel"
        when Consonant
            puts "#{letter} it's a consonant"
        else
            puts "#{letter} it's something else"
    end 

end
于 2011-05-23T19:44:25.217 回答
2

您让我感到困惑的代码，因为SimpleLetter应该是单个字母，而不是整个字母表。

尽管猴子补丁有点冒险，但我很想做以下事情：

module Voweliness
  def vowel?
    self =~ /[aeiou]/i
  end

  def consonant?
    (self =~ /[a-z]/i and not vowel?)
  end
end

class String
  include Voweliness
end


objects.each do |letter|
  case
    when letter.vowel?
      puts "#{letter} is a vowel"
    when letter.consonant?
      puts "#{letter} is a consonant"
    else
      puts "#{letter} is something else"
  end
end
于 2011-05-23T23:53:19.983 回答
1

你已经有几个很好的答案（例如sawa's），所以我只是为了好玩而没有case声明：

SIMPLE_LETTER = [*"a" .. "z"]
VOWEL        = %w[a e i o u]
CONSONANT    = SIMPLE_LETTER - VOWEL

[*?a..?f,*1..5].each do |letter|
  letter_class = %w(vowel consonant).select { |c| Object.const_get(c.upcase).include? letter}.first
  puts "'#{letter}': #{ letter_class || "something else"}"
end

输出：

'a': vowel
'b': consonant
'c': consonant
'd': consonant
'e': vowel
'f': consonant
'1': something else
'2': something else
'3': something else
'4': something else
'5': something else

multi-splat 和字符文字仅在 1.9 中有效。

于 2011-05-23T21:40:23.863 回答