til/ruby/iterate-with-an-offset-index.md

Iterate With An Offset Index

You can iterate over a collection of items with the #each method. If you want to know the index of each item as you go, you can use the #each_with_index variant.

> ["one", "two", "three"].each_with_index do |item, index|
    puts "#{item} - #{index}"
  end
one - 0
two - 1
three - 2
=> ["one", "two", "three"]

The initial index will always be 0 when using #each_with_index.

What about if you want the index value to be offset by some number?

You can use the #with_index method on an enumerator. It optionally takes an offset argument.

> ["one", "two", "three"].each.with_index(1) do |item, index|
    puts "#{item} - #{index}"
  end
one - 1
two - 2
three - 3
=> ["one", "two", "three"]