Question

I have a multi-dimensional array called my_ids_and_names
It should probably be a hash but lets leave it as an array for now 🙂

I create it with: my_own_array = Array.new[10],[2]

I have a variable @my_ids which has the id’s that I want.

I populate it within a method like this:

# Setup
@my_ids_and_names = Array.new[10],[2]
@my_ids.each do |cid|
  @my_ids_and_names[cid][1] = my_id
  @my_ids_and_names[cid][2] = MyModel.find(my_id).internal_name
end
@my_ids_and_names

Now I want to retrieve information in views.
I am trying:

<% @campaign_ids_and_names.each do |cid, nm| %>
  "various bits of code..."
  var_for_id = cid
  var_for_nm = nm
<% end %>

Will the cid and nm be set correctly?

I want the loop to be able to spit out the cid/names as in

id  name
4   brick
9   tile
45  grout

Right now I am getting The error occurred while evaluating nil.[]= in the setup

Answer 1

If you fire up irb console, you’ll see that Array.new[10],[2] is not creating an array you wanted, instead it creates the following array:

[nil, [2]]

If you want to create a new array with 10 array elements, use the following constructor:

Array.new(10, [])

Update 1

But as reading your question further I can see that you need a Hash instead of an Array, and you should keep in mind that ruby starts to index from 0 instead of 1.

So:

@my_ids_and_names = Hash.new
@my_ids.each do |cid|
  @my_ids_and_names[cid] = Array.new
  @my_ids_and_names[cid][0] = my_id
  @my_ids_and_names[cid][1] = MyModel.find(my_id).internal_name
end
@my_ids_and_names

Which can be further simplified to:

@my_ids_and_names = {}
@my_ids.each do |cid|
  @my_ids_and_names[cid] = [ my_id, MyModel.find(my_id).internal_name ]
end
@my_ids_and_names

Update 2

But that won’t work with your each loop what you’ve provided, so I would use the following code instead:

@my_ids_and_names = {}
@my_ids.each do |cid|
  @my_ids_and_names[cid] = MyModel.find(my_id).internal_name
end
@my_ids_and_names

This will create a Hash with cid keys and the internal_name of MyModels as values.