Last Updated: February 25, 2016
· msaspence

Activate HTML Elements Like a Boss in Ruby with Activated UI

active_link_to is a nice little gem to add an active class to your links based on the current url. The problems I had with this were I needed to manually specify which elements I wanted activated and I needed to activate elements that were not links.

I've had to solve this problem in three different codebases now so I figured it was time to move it out into its own gem, my first in fact:


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ActivatedUI, is a collection of helpers to set and manage the active state of UI elements. It is similar to active_link_to in that it is designed to help control the active state of UI elements for you. However where active_link_to infers the active state from the current url, ActivatedUI enables you to explicitly state it.


When installing for Rails 3 applications add this to the Gemfile: gem 'activated_ui' and run bundle install.

ActivatedUI should work without rails, but I have to admit I haven't really used it in this environment.


Setting the Active State

You can define the active state with:

activate_ui_marked :my_key # active state is [:my_key]

You can give it as many keys at a time as you like:

activate_ui_marked :my_key, :another_key # active state is [:my_key, :another_key]

activate_ui_marked builds on itself like so:

activate_ui_marked :my_key # active state is [:my_key]
activate_ui_marked :another_key # active state is now [:my_key, :another_key]

Getting the Active State

Once you have set the active state there are a number of ways you can use it:

Find if a key is active:

ui_activated? :my_key # will return true if :my_key is in the active state
ui_activated :my_key # ui_activated? is aliased to ui_activated if you so prefer

Find if multiple keys are active:

ui_activated? :my_key, :another_key # will return true if all of the arguments are in the active state

Get a html active class value:

<li class='<%= activated_class :my_key %>'>My Item</li> <!-- will produce class='active' if :my_key is in the active state otherwise class='' -->

By default the returned class is 'active', but you can change this:

self.class.activated_class 'my_active_class'
activated_class :key # will now return 'my_active_class'

With Rails

ActivatedUI isn't dependant on Rails but if you are using it with Rails here's how:

class ApplicationController < ActionController::Base
  include ActivatedUI

class PostsController < ApplicationController

  activate_ui_marked :posts # Adds :key to the active state using a call to before_filter
  activate_ui_marked :posts, :only => [:show] # It will pass on any options, so you can use before_filter's :only and :except options

  activated_class 'my_custom_active_class' # Change the return value of activated_class :key

  def show
    activate_ui_marked :show
    # show.html.erb


Activated UI will add activated_class, activate_ui_marked, stored_activated_ui, ui_activated? and ui_activated as view helpers:

<% if ui_activated? :posts %>
     <li class='<%= activated_class :show %>'><%= activated_link_to :show, "Show Posts", post_path(@post), class: 'btn' %></li>
<% end %>

It will also add a helper to wrap Rail's link_to:

<%= activated_link_to :show, "Show Posts", post_path(@post), class: 'btn' %>

It behaves the same way as link_to except there is an additional first argument that takes either a single key or an array of keys to check the active state with using ui_activated?. The active class is added to any classes you pass into via the options argument.