Ruby: Building a hash from a string and two array values at a time

Question

I'm trying to build a hash with:

hash = {}

strings = ["one", "two", "three"]

array = [1, 2, 3, 4, 5, 6]

so that I end up with:

hash = { "one" => [1, 2] ,
         "two" => [3, 4] ,
         "three" => [5, 6] }

I have tried:

strings.each do |string|
  array.each_slice(2) do |numbers|
    hash[string] = [numbers[0], numbers[1]]
  end
end

But that yields:

hash = { "one" => [5,6] , "two" => [5,6], "three" => [5,6] }

I know why it does this (nested loops) but I don't know how to achieve what I'm looking for.

score 14 · Accepted Answer · answered Nov 30 '11 at 21:07

14

If you want a one-liner:

hash = Hash[strings.zip(array.each_slice(2))]

For example:

>> strings = ["one", "two", "three"]
>> array = [1, 2, 3, 4, 5, 6]
>> hash = Hash[strings.zip(array.each_slice(2))]
=> {"one"=>[1, 2], "two"=>[3, 4], "three"=>[5, 6]}

answered Nov 30 '11 at 21:07

mu is too short

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+1 exactly what I was about to answer, but you beat me to it. :) – Mark Thomas Nov 30 '11 at 21:09
1

@mu is too short Never used the zip method before. That is pretty fantasticalicious. I love ruby. Thanks. – steve_gallagher Nov 30 '11 at 21:13
2

@steve_gallagher: [Enumerable](http://ruby-doc.org/core/Enumerable.html) is your friend, or at least it wants to be. – mu is too short Nov 30 '11 at 21:45

score 1 · Answer 2 · edited Nov 30 '11 at 22:52

1

hash = {}
strings.each { |string| hash[string] = array.slice!(0..1) }

This is a solution using methods and techniques you seem familiar with. It is not a 'one liner' solution but if you are new might be more understandable for you. The first answer is very elegant though.

edited Nov 30 '11 at 22:52

mu is too short

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answered Nov 30 '11 at 22:31

slindsey3000

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`strings.each_with_object({}) { |s,h| h[s] = array.shift(2) }` would be another version along similar lines. – mu is too short Nov 30 '11 at 22:51

score 0 · Answer 3 · answered Nov 30 '11 at 22:29

As Mu says, Zip method is the best choose:

Converts any arguments to arrays, then merges elements of self with corresponding elements from each argument. This generates a sequence of self.size n-element arrays, where n is one more that the count of arguments. If the size of any argument is less than enumObj.size, nil values are supplied. If a block is given, it is invoked for each output array, otherwise an array of arrays is returned.

Ruby: Building a hash from a string and two array values at a time

3 Answers3

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