how to use the method each_with_index in ruby, I wanna change the index of a given array

Question

I wanna change the index of a given array:

arr = ["cat", "tiger", "lion"]

so lion-item will have the value of 5-index, tiger will have value of 4-index and 3 for cat-item

is this possible?

Thanks!

how should the outcome look like? `[nil,nil,nil,"cat", "tiger", "lion"]`? — Uri Agassi, Jun 10 '14 at 12:29
@UriAgassi the same order but with using another order index, starting from 3 if u know wot I mean? — YoniGeek, Jun 10 '14 at 12:31
I don't think it is unclear, he want to access the elements based on another index so he doesn't have to convert the index every time. For example: `arr[3] #=> 'cat'`. — Patrick Oscity, Jun 10 '14 at 13:02

score 1 · Answer 1 · answered Jun 10 '14 at 12:30

1

You cannot do it with each_with_index, but you can do it with with_index.

arr.each.with_index(3) do |e, i|
  ...
end

answered Jun 10 '14 at 12:30

sawa

1

Yes.it is.. But OP's output is not clear . :) – Arup Rakshit Jun 10 '14 at 12:31

score 1 · Answer 2 · edited May 23 '17 at 10:32

1

Yes it's possible you can create a index method to acces it.

def get_by_index(array, value)
  array[value-3]
end

You can also create a new array child class who inherits from array and redefine an square bracket method as explained here:

edited May 23 '17 at 10:32

Community

answered Jun 10 '14 at 13:24

score 0 · Accepted Answer · answered Jun 10 '14 at 12:58

You could do that with a Hash:

hash = {
  3 => "cat",
  4 => "tiger",
  5 => "lion"
}

hash[4]
#=> "tiger"

If you want to convert from an Array to a Hash you can do this:

arr = ["cat", "tiger", "lion"]
hash = Hash[arr.each_with_index.map{|v,i| [i+3, v] }]
#=> {"cat"=>3, "tiger"=>4, "lion"=>5}

3 Answers3