Rails class_names(token_list)

Rails 6.1 introduces class_names helper | BigBinary Blog

Rails v6.0

<li class="<%= current_page?(dashboards_path) ? 'active' : '' %>">
  <%= link_to "Home", dashboards_path %>
</li>

Rails v6.1

<li class="<%= class_names(active: current_page?(dashboards_path)) %>">
  <%= link_to "Home", dashboards_path %>
</li>

class_names は token_list のエイリアス

ActionView::Helpers::TagHelper | RailsDoc(β)

token_list("foo", "bar")
 # => "foo bar"
token_list("foo", "foo bar")
 # => "foo bar"
token_list({ foo: true, bar: false })
 # => "foo"
token_list(nil, false, 123, "", "foo", { bar: true })
 # => "123 foo bar"

See also