See http://cjblomqvist.com/blog/Derby-Issue-with-arraylike-bindings-in-the-view-and-workaround/28 for info

gistfile1.txt

<Body:>
  <ul>{#each _page.unplannedOrder as :row}<li style="{#if _page.selected[:row.id]}background: red;{/}">{:row.id}</li>{/}</ul>
  <ul>{#each _page.unplannedOrder as :row}<li style="{#if multiplePartPath(_page.selected, :row.id)}background: red;{/}">{:row.id}</li>{/}</ul>