ERB template nested variable - accessing a hash key based on array element

Question

I have the following data and erb template: a hash mapping services to port numbers and an array of services.

I iterate over the array for each service and I need to access the hash to get the port number for the currently being processed service. I don't seem to be allowed to nest variables the way I am doing below. Is there a better way?

ports = {"max-api" => 83, "max-logger" => 82, "max-data" => 84}

services = %w( max_api max_data max_logger )

  <% @services.each do |service| %>
      <% if service.include?("max_logger") %>
        shell: echo <%= service %>:<%= @ports["<%= service %>"] %>
      <% else %>
        shell: echo <%= service %>:<%= @ports["<%= service %>"] %>00  
      <% end %>
  <% end %>

Simplest possible example I have the erb template

<% @services.each do |service| %>
<%= @ports[<%= service %>] %>
<% end %>

If I try to run my code I get the following error:

Chef::Mixin::Template::TemplateError
------------------------------------
(erubis):2: syntax error, unexpected '<', expecting ']'
 _buf << ( @ports[<%= service ).to_s; _buf << ']...
                   ^
(erubis):2: unterminated string meets end of file

Sorry to ask in such annoying way but, is it <%- service %> or <%= service %>?, include?('max_logger') or service == 'max_logger', is it @ports different to ports? — Sebastián Palma
– Sebastián Palma, Commented May 22, 2017 at 4:06
<%= service %> is the correct way, - was a mistake. The include statement for checking whether or not max_logger is being processed is correct. My understanding with @ports is that I need the @ for accessing externally defined variables that are passed to the erb. Therefore do not require it for service, which is defined within the erb template. — Brando__
– Brando__, Commented May 22, 2017 at 4:10
I see, help me to understand, if you check for the presence of a max_logger value within the array, then every value you iterate won't print 00, but if you check if such service == 'max_logger' then that will be just once, or more times if there are more than one 'max_logger' in @services. — Sebastián Palma
– Sebastián Palma, Commented May 22, 2017 at 4:12
What I am checking there is if the current iteration of services is max_logger. max_logger gets a special command ran that nothing else gets. max_logger will NOT print 00, but api and data WILL print 00. — Brando__
– Brando__, Commented May 22, 2017 at 4:16
My naming conventions are poor. Each service - api, logger, data - may actually run several daemons. Each daemon runs operates on a specific range of ports. What I really need to do is for each service is generate a config that includes all daemons. max_logger has the daemons max-logger and max-analytics, analytics being on port 1 and logger being on port 2. I may have oversimplified the examples in the original question if that isn't clear — Brando__
– Brando__, Commented May 22, 2017 at 4:19

Sebastián Palma · Accepted Answer · 2017-05-22 04:39:14Z

2

I realized lately they won't work if they don't match in name (array value, hash key):

{"max-api" => 83, "max-logger" => 82, "max-data" => 84}

They differ in - and/or _ from @services:

%w( max_api max_data max_logger )

Just tweaked a bit @services:

ports = {'max-api' => 83, 'max-logger' => 82, 'max-data' => 84}
services = %w(max-api max-data max-logger)

services.each do |service|
  puts "shell: echo #{service}:#{ports[service]}#{'00' if service != 'max-logger'}"
end
# => shell: echo max-api:8300
# => shell: echo max-data:8400
# => shell: echo max-logger:82

edited May 22, 2017 at 4:39

answered May 22, 2017 at 4:18

Sebastián Palma

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