Replace string if it contains one or more values included in an array

Question

I have a Ruby string, for instance: "blue green yellow dog cat mouse alpha beta".

I want to replace:

color names with the word "color",
animal names with the word "animal", and
greek letter names with the word "letter".

In other words, in my example above, I would like the new string to be:

"color animal letter"

and not

"color color color animal animal animal letter letter"

I came up with the following method:

def convert_string(string)
    if ["cat", "dog", "mouse"].include? key.to_s
      return "animal"
    end
    if ["blue", "yellow", "green"].include? key.to_s
      return "color"
    end
    if ["alpha", "beta"].include? key.to_s
      return "letter"
    end
    return key
end

How can I improve my method to achieve what I need?

Thanks, it works perfectly. Feel free to suggest this solution as an answer and I will gladly accept it. — Thibaud Clement
– Thibaud Clement, Commented Nov 16, 2015 at 5:25
If str = "alpha blue beta", what is the desired result? (That is, do you want to replace a run of animals, for example, with a single "animal"?) Can the string contain words that are not animals, colors or letters (e.g., "donuts")? — Cary Swoveland
– Cary Swoveland, Commented Nov 16, 2015 at 8:58
Your issue is not clear. Why does each replaced word appear only once? All instances of a kind are replaced with a single word? If so, in which position? I.e., should "blue cat green" become "color animal" or "animal color", or does it not matter? Or, do you replace only consecutive names of a kind into a word, giving you "color animal color" for "blue cat green"? — sawa
– sawa, Commented Nov 16, 2015 at 10:44

suslov.nikita · Accepted Answer · 2015-11-16 05:29:26Z

2

You can use gsub:

str = "blue green yellow dog cat mouse alpha beta"

str.gsub(/(cat|dog|mouse)/, 'animal')
   .gsub(/(blue|yellow|green)/, 'color')
   .gsub(/(alpha|beta)/, 'letter')
   .split.uniq.join ' '

answered Nov 16, 2015 at 5:29

suslov.nikita

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2 Comments

Cary Swoveland Over a year ago

If str = "alpha blue beta", this returns "letter color". I assume that "letter color letter" is wanted, but clarification is required.

Thibaud Clement Over a year ago

Thanks for your comment @CarySwoveland. In your example, we do want "letter color" and not "letter color letter", which is why I accepted the anwser of @potashin.

Cary Swoveland · Accepted Answer · 2015-11-16 17:42:42Z

Suppose:

str = "gamma blue green yellow dog cat mouse alpha beta"

Notice that str is slightly different than the example given in the question.

I've assumed that you want to replace each run of colors (or animals or letters) in the string by the word "color" (or "animals" or "letters").

Here are two ways to do that.

#1

This uses Enumerable#chunk and Object#itself. The latter was introduced in v.2.2. For earlier versions, write ...chunk { |s| s }....

str.split.map do |word|
  case word
  when "blue", "green", "yellow"
    "color"
  when "dog", "cat", "mouse"
    "animal"
  when "alpha", "beta", "gamma"
    "letter"
  end
end.chunk(&:itself).map(&:first).join(' ')
  #=> "letter color animal letter"

map returns:

#=> ["letter", "color", "color", "color", "animal",
#    "animal", "animal", "letter", "letter"]

which is then chunked. Denoting this array as arr, an alternative to chunking is:

arr.each_with_object([]) { |w,a| a << w if a.empty? || w != a.last }

#2

COLOR  = "color"
ANIMAL = "animal"
LETTER = "letter"

h = { COLOR  => %w{ blue green yellow },      
      ANIMAL => %w{ dog cat mouse },
      LETTER => %w{ alpha beta gamma } }.
      each_with_object({}) { |(k,v), h| v.each { |item| h[item] = k } }
 #=> {"blue"=>"color", "green"=>"color", "yellow"=>"color",
 #    "dog"=>"animal", "cat"=>"animal", "mouse"=>"animal",
 #    "alpha"=>"letter", "beta"=>"letter", "gamma"=>"letter"}

r = /
    \b        # match a word break
    (\w+)     # match a word in capture group 1
    (?:\s\1)+ # match one or more copies of the matched word, each preceded by a space
    \b        # match a word break
    /x        # extended or free-spacing mode

str.gsub(/\w+/,h).gsub(r,'\1')
  #=> "letter color animal letter"

or

str.split.map { |word| h[word] }.chunk(&:itself).map(&:first).join(' ')
  #=> "letter color animal letter"

Thanks for your answer. Please see my comment on @potashin's answer for clarification.

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