How to render an array in Rails

Question

In my Rails application, I have a class Bar and a controller FooController.

class Bar
   attr_accessor :id
end

class FooController < ApplicationController
   def index
      @rows = {}
      bar = Bar.new
      bar.id = 1
      @rows[0] = bar

      render "index"
   end
end

In the view, I would like to render like this

<table>
<% @rows.each do |bar| %>
  <tr>
    <td><%= bar.id %></td>
  </tr>
<% end %>  
</table>

But it will throws error

undefined method `id' for [0, #<Bar:0x00007fc65db33320 @id=1>]:Array

If I render like this:

<%= @rows %>

the raw data of the array @rows will be rendered as:

{0=>#<Bar:0x00007fc65db33320 @id="1">}

How do I render the elements one by one?

With the code you have shown, it should not be throwinng that undefined method error. Are you sure it's coming from that line? — max pleaner
– max pleaner, Commented Feb 14, 2019 at 9:31
Your example and its output don't match. According to your code (@rows[0] = bar), the "raw data" should have a key of 0, not 1. Please provide a valid example and also include the whole error message, including the error's line number. — Stefan
– Stefan, Commented Feb 14, 2019 at 9:47
@Stefan: Yes you are right. Sorry again. I have just corrected it in the question. — kbisang
– kbisang, Commented Feb 14, 2019 at 10:29
@kbisang it makes much more sense now, thanks for taking the time to edit the question! — Stefan
– Stefan, Commented Feb 14, 2019 at 11:54

spickermann · Accepted Answer · 2019-02-14 09:33:14Z

1

The problem is that @rows = {} doesn't assign an array but a hash. And therefore @rows[0] = bar doesn't store bar as the first element in the array, but it stores bar under the key in the hash.

Just change your controller method to:

def index
  @rows = []

  bar = Bar.new
  bar.id = 1

  @rows << bar

  render "index"
end

answered Feb 14, 2019 at 9:33

spickermann

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8 Comments

Stefan Over a year ago

Doesn't explain the "undefined method 'each' for nil:NilClass" error – hash does respond to each.

kbisang Over a year ago

Great, that helps! Thanks Spickermann for your correct answer.

kbisang Over a year ago

the problem was that I filled the array @rows like this @rows[0] = bar instead of @rows << bar

Stefan Over a year ago

@kbisang I don't see how that could result in the given error message.

Stefan Over a year ago

@kbisang what do you mean? If i have @rows = {} and @rows[0] = 'foo', then @rows.each { ... } doesn't give an error. Hashes can be traversed via each just fine (of course).

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