Iterating over an array to create variables in ruby

Question

Is it possible to create multiple variables by iterating over an array?

For example, say I had an array called numbers = [1,2,3,4,5] and I wanted to create a series of variables called number_1, number_2,...,number_5 each equal to their respective index in the numbers array (e.g. number_1 = 1, number_2 = 2, etc.).

I tried something along the lines of the following:

numbers.each_with_index do |num, index|
  number_"#{index+1}" = num
end

But that failed.

Essentially, I would like for the iterating process to automate creating and assigning values to variables.

Thank you.

Why do you want to do this? What does number_1 give you that numbers[0] doesn't? — ptd
– ptd, Commented Jan 16, 2015 at 22:08
This will probably meet your needs: stackoverflow.com/q/16419767/2177 — yalestar
– yalestar, Commented Jan 16, 2015 at 22:11

joelparkerhenderson · Accepted Answer · 2015-01-16 22:17:29Z

2

One way is:

instance_variable_set("@number_#{index+1}", num)

Another way is using the eval method to create an instance variable:

eval "@number_#{index+1} = #{num}"

Heads up that eval is considered a bit hacky, and doesn't work on JRuby.

(Caveat: the code above creates instance variables, not scope-level variables (a.k.a. local variables). Example: the code creates @number_1 not number_1. As far as I'm aware Ruby does not offer a straightforward way to dynamically create a scope-level variable that persists; you can create one within an eval but it goes out of scope beyond the eval.)

edited Jan 16, 2015 at 22:17

answered Jan 16, 2015 at 22:12

joelparkerhenderson

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1 Comment

ptd Over a year ago

Note that this will not create local variables (as seems to have been requested). There is no way to create local variables in this way.

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