How to tag with acts-as-taggable-on in Rails 5

If you want to add tags, categories, filters, and so on, to your Rails 5 models, the acts-as-taggable-on gem is the way to go. Using it with Rails 5 is fairly straightforward.

1. Add it to your Gemfile:

gem 'acts-as-taggable-on', '~> 6.0'

2. Run bundle install.

3. Install its migrations:

rake acts_as_taggable_on_engine:install:migrations

4. Run rake db:migrate.

5. Add acts_as_taggable_on to your model. You don’t need to create a migration for your tags – acts-as-taggable-on handles that for you. You can change :tags to anything you’d like – :categories, :codes, etc.

# post.rb
class Post < ApplicationRecord
acts_as_taggable_on :tags

6. Then, inside your controller, you’ll need to accept :tag_list (or :category_list, or :code_list, etc.) as a strong param. It’s the singular version of the word you used in your model, appended with _list.

# posts_controller.rb
class PostsController < ApplicationController
# ...

def post_params
params.require(:post).permit(:title, :body, :tag_list)

7. Now you can add the tags to a form. Sometimes, you may be able to get away with <%= f.input :tag_list %>, but I’ve had to use a slightly more complicated version in the past. Users can add multiple tags by separating them with commas:

<!-- views/posts/_form.html.erb -->
<%= form.label :tag_list, "Tags" %>
form.text_field :tag_list,
value: @post.send(:tag_list).to_s,
placeholder: 'rails, development'

8. You can search by tagged filters, as well:

# routes.rb
get '/tagged', to: "posts#tagged", as: :tagged

# posts_controller.rb
def tagged
if params[:tag].present?
@posts = Post.tagged_with(params[:tag])
@posts = Post.all

9. And then list each post, plus the option to sort by tags in your view:

<!-- views/posts/index.html.erb -->
<% @posts.each do |p| %>
<h2><%= p.title %></h2>
<div class="tags">
<% p.tag_list.each do |t| %>
<%= link_to t, tagged_path(tag: t) %>
<% end %>
<% end %>

Once you understand how it works, acts-as-taggable-on is a pretty easy gem to use. It has a lot of other features, as well, that you can learn more about on its GitHub page. Have fun tagging!

About the author

I'm Mark Thomas Miller, a full stack engineer and designer currently working at ConvertKit. (We're hiring!) People like Arnold Schwarzenegger, Lindsey Stirling, and Tim Ferriss use features I've built to connect with their fans. I'm currently geeking out about Svelte, mechanical keyboards, and minimalist UI design, and replaying Ocarina of Time.