Mapping and choosing from an array of arrays(which is just a pair of elements). Ruby

I have this array:

[["A", 0], ["B", 0], ["b", 0], ["F", 1], ["G", 2], ["g", 3], ["C", 0]]

and I want to choose from the pair if it's 0 or not and create a new array that results into this

["A","B","b",1,2,3,"C"]

I tried using

arr.each do |a| 
  if a.last == 0
    a.first
  else
    a.last
  end
end

but it returns the original array.

You are really close. Just use map instead of each. each just loops through the Enumerable it is called on and returns the original object. map also loops through the Enumerable but returns an Array of result values of those iterations.

To pass a different value as a result value of an iteration block than a return value of its last command use next. Calling next value will stop processing the current loop with value as its result.

Your working code is:

arr = [["A", 0], ["B", 0], ["b", 0], ["F", 1], ["G", 2], ["g", 3], ["C", 0]]
new_arr = arr.map do |a| 
  if a.last == 0
    a.first
  else
    a.last
  end
end
#=>  ["A", "B", "b", 1, 2, 3, "C"]

A code example using next

arr = [["A", 0], ["B", 0], ["b", 0], ["F", 1], ["G", 2], ["g", 3], ["C", 0]]
new_arr = arr.map do |a| 
  next a.first if a.last == 0
  a.last
end
#=>  ["A", "B", "b", 1, 2, 3, "C"]

instead of #each or even map you could also use #each_with_object, you could pass in any object of your choice but sounds like you want an array here is an example

new_array = input.each_with_object([]) do |a, arr|
  # the second value `arr` passed to the block is the []
  arr << if a.last.zero?
   a.first
  else
    a.last
  end
end
#=>  ["A", "B", "b", 1, 2, 3, "C"]