simple-form makes creating forms that handle associations in rails a breeze. It creates a select dropdown that works really well for use cases where the number of records are few. But once the number of options in the select box gets over a certain number you would be doing your users a favor by implementing it an autocomplete box.

I ran into the same situation. I had a Contact table that has_one: Panchayat relation. I used simple_form to create the association select dropdown. I wanted to add autocomplete capabilities to it. The rails autocomplete libraries were either outdated or neede jQuery to support. I even asked on StackOverflow https://stackoverflow.com/questions/60520237/how-to-implement-autocomplete-for-association-in-simple-form-in-rails-6?noredirect=1#comment108147660_60520237 with no avail. After some more digging I used a raw javascript library all thanks to the new webpack integration of Rails.

Meet Choices

Choices is a native JS libary with no dependencies that are designed for handling select boxes. Read more at https://joshuajohnson.co.uk/Choices/

Setting up

• Install Choices with yarn add choices.js in the project repo. The new webpack pipeline of Rails would handle all the bundling of the js code.

• In your application.js file add the below code. This would replace all the occurence of the class #dropdown-choice-select with the choice dropdown. Create a new css/application.css file in the javascript folder.

  // Import css from js for webpack to process it correctly
  import '../css/application.css'
  
  // Add Choices Dropdown
  const Choices = require('choices.js')
  document.addEventListener("turbolinks:load", function() {
  var dropDownSelects = new Choices('#dropdown-choice-select')
  })

• In your application.css file add the below line

  @import "choices.js/public/assets/styles/choices.css";

Using it

To use it in a form to prefill an association all you have to do is

<%= f.association :assoc_name, collection: Assoc.all(), input_html: {id: 'dropdown-choice-select'} %>

Choice would do it’s magic and convert it into an awesome autocomplete select box.

For reference https://github.com/coronasafe/coronacell/