Refactoring for image versions and rails transforming locals for partials into symbols

Question

Using the carrierwave gem to generate various versions of images, these can be invoked to generate the required image by referring to its version name

style='background: url(<%= pict.image_url(:small).to_s %>);'

Integrating these to a framework, such as foundation, that handles the viewports

<div class='show-for-small-only'>
  <%= render partial: 'items', locals: { size: 'small'} %>
</div>
<div class='show-for-medium-only'>
  <%= render partial: 'items', locals: { size: 'medium'} %>
</div>

How can one invoke the local as a symbol, as the following generates a syntaxic error

style='background: url(<%= pict.image_url(:#{size}).to_s %>);'

Answer 1

the proper call has two sets of renderings and thus the inner one requires double quotes for interpretation:

style='background: url(<%= pict.image_url("#{size.to_sym}").to_s %>);'