CODEWITHSUNDEEP
arraysrubystring
Jake Cooper
Jake Cooper

Reputation: 121

Storing string in arrays in ruby

I am attempting to write a method that changes one string to another one letter at a time. However, I never noticed in ruby that if you push a string variable to an array it seems to push the address of the string variable and not the string.

def mutate_my_strings(s1,s2)
  #your code here

  str1 = s1.to_s
  str2 = s2.chars
  ret = []

  puts str1
  ret.push(str1)

  s1.chars.each_with_index do |q,idx|
    str1[idx] = str2.shift    
    ret.push(str1)
  end
  return ret.join("\n")
end

mutate_my_strings("bubble gum", "turtle ham")

This output shows that the enumerable modifies the str1 but the out for the puts the string "bubble gum" turn into "turtle ham" This isn't so in the array. The entire string is modified in the array:

bubble gum
"tubble gum"
"tubble gum"
"turble gum"
"turtle gum"
"turtle gum"
"turtle gum"
"turtle gum"
"turtle hum"
"turtle ham"
"turtle ham"
=> "turtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham\nturtle ham"

Upvotes: 2

Views: 85

Answers (2)

Danil Speransky
Danil Speransky

Reputation: 30473

Replace ret.push(str1) with ret.push(str1.dup) to create a new string every time.

And here is a more elegant solution to the problem:

def mutate_strings(s1, s2)
  (0...s1.size).map { |i| s2[0..i] + s1[i+1..-1] }.join("\n")
end

puts(mutate_strings('bubble gum', 'turtle ham'))

Upvotes: 1

Jake Cooper
Jake Cooper

Reputation: 121

I fix it by adding:

ret.push(str1) to
ret.push(str1 * 1)

This creates a new pointer every iteration

Upvotes: 0

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