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[英]In Ruby is there an alternative and more elegant way to call a method than 'case - when'?
[英]Is there a more functional way, than using custom case statements, to write this in Ruby?
想象一下下面的代碼:
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
我本可以選擇任何其他類,我只是以它們為例。 我非常喜歡 Scala 的match
和提取器,我認為這可能是在 Ruby 中編寫相同內容的好方法。 有沒有更好的方法來編寫上面的內容而不必實例化新對象,這樣我就可以調用他們的===
方法?
只是為了避免不必要的帖子,是的,我知道我可以這樣做:
case letter
when ["a","e","i","o","u"].include?(letter)
# ...
end
你不需要角色的類。 將它們設置為 arrays,並在 case 語句中使用 splat 運算符。
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
===
也適用於塊:
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
您可以使用 class 方法而不是實例方法:
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
您讓我感到困惑的代碼,因為SimpleLetter
應該是單個字母,而不是整個字母表。
盡管猴子補丁有點冒險,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
你已經有幾個很好的答案(例如sawa's),所以我包括一個只是為了好玩而沒有case
陳述的答案:
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
Output:
'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 和字符文字僅在 1.9 中有效。
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