Understanding options_for_select with a map in Rails

Question

<form id="earnings_select" action="<%= publishers_earnings_statements_url %>" method="get">
  <% unless current_publisher.earnings_statements.all.size == 0 %>
    <%= select_tag 'id', 
                   options_for_select(current_publisher.earnings_statements.all.map{|s| [s.label, s.id.to_s]}, params[:id]),
                   :id => 'earnings_select_id' %>  
    <input type="submit" value="Go">
  <% end %>
</form>

That's the code that I have... can someone please explain what the current_publisher.earnings_statements.all.map{|s| [s.label, s.id.to_s]} bit is for?

I'm not a Rails expert and having a hard time understanding what it means. Any help would be greatly appreciated.

Thanks

Answer 1

Map creates a new array based on what's returned by the block passed to it. In this case it returns an array of arrays which contains the label and id from earning_statements. It would look something like

[[label1, id1], [label2, id2]]

This array is then used as options for the select tag. The label being the text displayed and the id being the reference to which choice the user makes.