Ruby each_with_index offset

Can I define the offset of the index in the each_with_index loop iterator? My straight forward attempt failed:

some_array.each_with_index{|item, index = 1| some_func(item, index) }

Edit:

Clarification: I don't want an array offset I want that the index within the each_with_index doesn't start from 0 but e.g. 1.

Solution 1:

Actually, Enumerator#with_index receives offset as an optional parameter:

[:foo, :bar, :baz].to_enum.with_index(1).each do |elem, i|
  puts "#{i}: #{elem}"
end

outputs:

1: foo
2: bar
3: baz

BTW, I think it is there only in 1.9.2.

Solution 2:

The following is succinct, using Ruby's Enumerator class.

[:foo, :bar, :baz].each.with_index(1) do |elem, i|
    puts "#{i}: #{elem}"
end

output

1: foo
2: bar
3: baz

Array#each returns an enumerator, and calling Enumerator#with_index returns another enumerator, to which a block is passed.

Solution 3:

1) The simplest is to substitute index+1 instead of index to the function:

some_array.each_with_index{|item, index| some_func(item, index+1)}

but probably that is not what you want.

2) The next thing you can do is to define a different index j within the block and use it instead of the original index:

some_array.each_with_index{|item, i| j = i + 1; some_func(item, j)}

3) If you want to use index in this way often, then define another method:

module Enumerable
  def each_with_index_from_one *args, &pr
    each_with_index(*args){|obj, i| pr.call(obj, i+1)}
  end
end

%w(one two three).each_with_index_from_one{|w, i| puts "#{i}. #{w}"}
# =>
1. one
2. two
3. three

This answer, which was answered a few years ago, is now obsolete. For modern Rubies, Zack Xu's answer will work better.

Solution 4:

If some_index is somehow meaningful, then consider using a hash, rather than an array.

Solution 5:

I ran into it.

My solution not necessary is the best, but it just worked for me.

In the view iteration:

just add: index + 1

That's all for me, as I don't use any reference to those index numbers but just for show in a list.