Rails Active Link Helper

application_helper.rb

module ApplicationHelper
  def app_link_to(name, url, html_options, active_options)
    css_class = html_options[:class].split(' ')

    if params[:controller] == active_options[:controller]
      css_class << active_options[:active_class]
    end

    html_options[:class] = css_class.join(' ')

    link_to(name, url, html_options)
  end
end

example.html.erb

<%= app_link_to 'Clients',
                clients_path,
                { class: 'navigation__app--link' },
                controller: 'clients',
                active_class: 'selected'
%>

A simple example of how to extend the build in link_to helper to highlight links in your application. This is not intended to be a drop in solution for every case but it's a good place to start.