Blacklight has added support for view components. While there are several benefits to using this abstraction, the major benefit for Blacklight (as a Rails engine) the ability to define an explicit interface to views to make them easier and safer to override.
A good example of this new abstraction is the new configuration parameter available for facets:
config.add_facet_field 'format', label: 'Format', component: SuperSpecialFacetComponent
This tells Blacklight to use your custom component for rendering the facet (similar in some ways to the partial configuration). This component will get handed a Blacklight::FacetFieldPresenter instance, and it’s responsible for rendering everything about the facet control.
We can start implement this component (in app/components/super_special_facet_component.rb) by inheriting the existing behavior:
class SuperSpecialFacetComponent < Blacklight::FacetFieldListComponent
end
For this example, we want to customize the display of the facet, so we’ll need to add a corresponding app/components/super_special_facet_component.html.erb. We’ll start from the current list view:
<%= render(@layout.new(facet_field: @facet_field)) do |component| %>
<% component.with(:label) do %>
<%= @facet_field.label %>
<% end %>
<% component.with(:body) do %>
<ul class="facet-values list-unstyled">
<%= render_facet_limit_list @facet_field.paginator, @facet_field.key %>
</ul>
<% end %>
<% end %>
and then make a nice visible change:
<% component.with(:label) do %>
- <%= @facet_field.label %>
+ -> <%= @facet_field.label %> <-
<% end %>
Note: the view_component gem is aggressive about caching lookup paths, so if you’re not seeing the updated label, try restarting your Rails application.
We get @layout from the upstream component (also separately configurable using layout, but defaults to Blacklight::FacetFieldComponent, which provides the expand/collapse behavior). We can plug any custom rendering into the different content areas provided by the layout (label and body).