Ruby convert string formatted as multidimensional array, to actual Array

Question

I have a string in Ruby:

[[nil,nil,nil,nil,nil,nil,nil,nil,nil,'Average of','Transaction Amount','dataset_test_3.SampleData100'],[nil,nil,nil,nil,nil,nil,nil,nil,nil,nil,'Country','dataset_test_3.SampleData100']]

It is formatted perfectly as a multidimensional Array, and has 2 sub-arrays. (in some cases, it may have 3).

How can I create an actual Array out of this?

Appreciate any directions, have been look for a while on this to no avail whatsoever.

When supplying data, please reduce it to the bare minimum necessary to reproduce the problem you're seeing. Anything else beyond that is a waste of our time. Your question sounds like an XY question, where you're asking about question Y, when you should be asking about X. How did you get that string representation of the an array? That's very rare and usually is the result of trying to use the output of inspect or capturing a puts-type output. — the Tin Man
– the Tin Man, Commented Sep 12, 2014 at 15:55
If you could use a neutral format like JSON your life would be a lot easier. — tadman
– tadman, Commented Sep 12, 2014 at 16:29

the Tin Man · Accepted Answer · 2014-09-12 16:01:38Z

2

You can also use YAML to parse your string into an array

require 'yaml'

array = YAML.load(input)
array.flatten 
# => ["nil", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "Average of", "Transaction Amount", "dataset_test_3.SampleData100", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "nil", "Country", "dataset_test_3.SampleData100"]

edited Sep 12, 2014 at 16:01

the Tin Man

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answered Sep 12, 2014 at 15:56

usha

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2 Comments

Hendrik Kleine Over a year ago

Almost! If I do this though, the nil values in my string remain strings. I've tried to make them nil with gsub, like below, but it given an error. array.each do |s| s.gsub('\"nil\"',nil) end

DBrown Over a year ago

Still brilliant to this day! I was passing a 2D array of integers via CLI to another process, and as long as I planted the entire array into a single string, this was the perfect method for converting it back to an array of integers. Cheers!

Community · Accepted Answer · 2017-05-23 12:24:24Z

2

The answer for your question is eval().

You can use eval() to evaluate a string as "code" in ruby.

For example, in your case, if you have this string called input, which contains an array declaration then:

b = eval(input)
b # => [[nil,nil,nil,'Average of',....]]

Here is a great introduction for eval() from RubyMonk:

http://rubymonk.com/learning/books/5-metaprogramming-ruby-ascent/chapters/24-eval/lessons/63-eval

And after eval(), you can use flatten on your array, to flat it out to a one dimension one.

So, in short, eval(input).flatten would do the job. :) ( as Nimir suggested)

It's also worth noting this can be extremely dangerous to do on untrusted data. DO NOT ever evaluate arbitrary user data. (by tadman )

edited May 23, 2017 at 12:24

CommunityBot

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answered Sep 12, 2014 at 15:39

kriskova

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3 Comments

Hendrik Kleine Over a year ago

My string is named "input". If I do input.flatten, I get this error: undefined method `flatten' for #<String:0x00000000fdceb0> (NoMethodError)

the Tin Man Over a year ago

You can't flatten a String.

tadman Over a year ago

It's also worth noting this can be extremely dangerous to do on untrusted data. DO NOT ever evaluate arbitrary user data.

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