CODEWITHSUNDEEP
rubyruby-on-rails-3iterator
Codejoy
Codejoy

Reputation: 3816

each_with_index_do starting at 1 for index

I am using a ruby iterator on a view in a rails app like so:

<% ([email protected]).each_with_index do |element, index| %>
  ...
<% end %>

I thought the addition of the 1.. instead of just saying: @document.data

would get the trick of having the index above start at 1. But alas, the above code index is still 0 to data.length (-1 effectively). So what am I doing wrong, i need the index to equal 1-data.length...no clue how to set up the iterator to do this.

Upvotes: 43

Views: 58345

Answers (9)

Igor
Igor

Reputation: 1311

For anyone who came here looking for each_with_index starting at an offset - You are looking for with_index.

change each_with_index to each.with_index(2) for starting with index 2

Upvotes: 0

Tyler Rick
Tyler Rick

Reputation: 9491

Unless you're using an older Ruby like 1.8 (I think this was added in 1.9 but I'm not sure), you can use each.with_index(1) to get a 1-based enumerator:

In your case it would be like this:

<% @document.data.length.each.with_index(1) do |element, index| %>
  ...
<% end %>

Upvotes: 157

worrawut
worrawut

Reputation: 1068

This may not be exactly the same each_with_index method in question, but I think the result may close to something in mod is asking...

%w(a b c).each.with_index(1) { |item, index| puts "#{index} - #{item}" }

# 1 - a
# 2 - b
# 3 - c

For more information https://ruby-doc.org/core-2.6.1/Enumerator.html#method-i-with_index

Upvotes: 12

fullstackplus
fullstackplus

Reputation: 1071

Use Integer#next:

[:a, :b, :c].each_with_index do |value, index|
  puts "value: #{value} has index: #{index.next}"
end

produces:

value: a has index: 1
value: b has index: 2
value: c has index: 3

Upvotes: 10

Eirik Coppa Thommessen
Eirik Coppa Thommessen

Reputation: 11

I had the same problem, and solved it by using the each_with_index method. But added 1 to the index in the code.

@someobject.each_with_index do |e, index|
   = index+1

Upvotes: 0

sameera207
sameera207

Reputation: 16619

If I understand your question right, you want to start the index from 1, but in ruby arrays goes as 0 base indexes, so the simplest way would be

given @document.data is an array

index = 1
@document.data.each do |element| 
    #your code
    index += 1
end

HTH

Upvotes: 1

Matthew Rudy
Matthew Rudy

Reputation: 16834

I think maybe you misunderstand each_with_index.

each will iterate over elements in an array

[:a, :b, :c].each do |object|
  puts object
end

which outputs;

:a
:b
:c

each_with_index iterates over the elements, and also passes in the index (starting from zero)

[:a, :b, :c].each_with_index do |object, index|
  puts "#{object} at index #{index}"
end

which outputs

:a at index 0
:b at index 1
:c at index 2

if you want it 1-indexed then just add 1.

[:a, :b, :c].each_with_index do |object, index|
  indexplusone = index + 1
  puts "#{object} at index #{indexplusone}"
end

which outputs

:a at index 1
:b at index 2
:c at index 3

if you want to iterate over a subset of an array, then just choose the subset, then iterate over it

without_first_element = array[1..-1]

without_first_element.each do |object|
  ...
end

Upvotes: 37

Kyle
Kyle

Reputation: 22258

An array index is always going to be zero based.

If you want to skip the first element, which it sounds like you do:

@document.data[1..-1].each do |data|
   ...
end

Upvotes: 1

Sully
Sully

Reputation: 14943

There is no such thing as making the index start from 1. If you want to skip the first item in the array use next.

<% ([email protected]).each_with_index do |element, index| %>
  next if index == 0
<% end %>

Upvotes: 2

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