Suppose the controller is FoosController and the action of index page for current_user is #bar, then your controller may look like this
class FoosController < ApplicationController
def bar
@user = current_user
end
To reuse the template, you can make a separate partial template say app/views/foos/_index.html.erb
.
Then, in app/views/foos/bar.html.erb
<%= render partial: '_index', locals: { user: @user }
To reuse the partial template in another action, you just need to call the partial in another template, feed it with different instance variable.