Using variables in an array passed to a def - Rails

Question

I'm using the Google charts API to generate a pie chart in my Rails application. However, I'm having a problem passing local variables to the def in the helper. The def takes a 2D array of [label, value] pairs. It doesn't like it when I try to pass a local variable in as the value. These are calculated ahead of time and are in currency format. Putting the variable in quotes or in #{} doesn't work either.

application_helper.rb

  def pie_chart(data, options = {})
    options[:width] ||= 250
    options[:height] ||= 100
    options[:colors] = %w(F5DD7E 0DB2AC FC8D4D FC694D FABA32 704948 968144 C08FBC ADD97E)
    dt = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-."
    options[:divisor] ||= 1
    options[:title] ||= "Energy Costs"

    while (data.map { |k,v| v }.max / options[:divisor] >= 4096) do
      options[:divisor] *= 20
    end

    opts = {
      :cht => "p",
      :chd => "e:#{data.map{|k,v|v=v/options[:divisor];dt[v/64..v/64]+dt[v%64..v%64]}}",
      :chl => "#{data.map { |k,v| CGI::escape(k)}.join('|')}",
      :chs => "#{options[:width]}x#{options[:height]}",
      :chco => options[:colors].slice(0, data.length).join(','),
      :chf => "bg,s,FFFFFF00",
      :chtt => "#{options[:title]}"
    }

The def call in the view:

<%= pie_chart( [["Light Cost", #{light_cost}], ["Small Appliance Cost", #{sm_appl_cost}]], :width => 550, :height => 200) %>

How do I pass the local variables?

Answer 1

What's the error you get? You should be able to call it like:

<%=
  pie_chart(
    [
      ["Light Cost", light_cost],
      ["Small Appliance Cost", sm_appl_cost]
    ],
    { :width => 550, :height => 200 }
  )
%>

I added {}'s around the hash just to make it clearer and explicit.

Using #{var} is not the way to do it here because that's for substitution in a string, eg "Here is the value: #{var}".

Answer 2

So that code definitely wants numeric values, but #{} is just going to start a comment unless used inside a string, and you don't want a string there.

And actually, pie_chart as written would appear to take either a 2D array as you say OR a Hash, if the only use of it is with 2-variable .map iterators. So you should be able to use either [["str1", light_cost], ["str2", sm_appl_cost]] or { 'str1'=>light_cost, 'str2'=>sm_appl_cost}.

You do need to make sure that those locals are numeric, though. Try using .to_i or .to_f on them if they aren't.