Grouped table
How this page is built
the gem renders it — this is all you write
Grouping is a render-time arrangement, like the layout. Add group_by: :publisher — the gem orders by the group key, splits the rows into collapsible groups (chevron in the header) and shows a per-group count. With 120 books, groups start collapsed beyond config.group_collapse_threshold (default 50), opening only the first; the open ones live in ?open=, so a half-expanded view is copy-pasteable.
app/views/groups/index.html.erb
<%= crud_collection @books, group_by: :publisher %> <%# belongs_to, enum or a column %>Read more: Grouping
