Dynamic dropdown in rails simple_form

Question

I have a simple has_many and belongs_to relationship in my rails app. I'm using simple_form and want to dynamically change the dropdown options based on the value chosen by the user.

Models

 class Processor < ApplicationRecord
   has_many :processor_bank_accounts
 end

 class ProcessorBankAccount < ApplicationRecord
   belongs_to :processor
 end

Form inputs

<%= simple_form_for [@customer, @transaction] do |f| %>
<%= f.error_notification %>

<div class="form-inputs">
  <%= f.input :status, :collection => ["payment request"], include_blank: false %>
  <%= f.input :processor, collection: @processors ,label_method: :name,value_method: :id,label: "Processor" , include_blank: false %>
  <%= f.input :processor_bank_account, collection: @bank_accounts , label_method: :bank_name, value_method: :id, label: "Processor Bank Account" , include_blank: true %>
  <%= f.input :tcurrency, collection: @currencies, include_blank: false, label: 'currency' %>
  <%= f.input :amount, as: :decimal, label: 'amount' %>
</div>

<div class="form-actions text-center">
  <%= f.button :submit, "Add transaction", class: "form-button"%>
</div>
<% end %>

So essentially, I need the processor_bank_account dropdown to populate based on the processor chosen by the user. In the console, this would just be: ProcessorBankAccount.where(processor: processor).

Need to load options using JS and think I need to use JSON but not sure where to go from here

David · Accepted Answer · 2018-09-18 10:02:37Z

One way to do this would be to use jQuery to make an AJAX call to a controller action and then let Rails handle the rest through an erb template.

So on your page, with the form, invoke the action via AJAX using something like:

<script>
    $(document).ready(function() {
        $('#processor_id').on('change', function() {
            $.ajax({
                url: '/transactions/get_processor_bank_accounts',
                type: 'GET',
                data: {
                    processor_id: this.value
                },
                dataType: 'script',
                error: function() {
                    alert('An error occurred retrieving bank accounts for the selected processor.');
                }
            });
        });
    });
</script>

NB, #processor_id is the id for your dropdown control.

Next, instantiate the bank accounts within your action in your controller:

def get_processor_bank_accounts
  @processor_bank_accounts = ProcessorBankAccount.where(processor_id: params[:processor_id])
end

And finally simply create a view that will be responsible for repopulating your dropdown:

$select_list = $('#processor_id');
$select_list.empty();

<% @processor_bank_accounts.each do |pba| %>
  $select_list.append($('<option value="<%= pba.id %>"><%= pba.name %></option>'));
<% end %>

rhosyn · Accepted Answer · 2018-09-18 14:49:52Z

I came up with the following solution:

1) Add a new method to my processors controller to render the inputs for the second (dynamic) dropdown in JSON format:

def processor_bank_accounts
 render json: @processor.processor_bank_accounts.each do |bap|
 { id: bap.id, name: bap.name }
 end
end

2) Assign this new function to a new route in config/routes:

get 'api/bankaccounts', to: 'processors#processor_bank_accounts', as: 'bankaccounts'

3) Create a JS function to access the route with the id of the processor selected in the first dropdown and populate the second dropdown with items from the JSON array:

// select first dropdown
const processor = document.getElementById("transaction_processor");
// select second dropdown
const bapSelect = document.getElementById("transaction_processor_bank_account");

function update_baps(processor_id) {
 const url = `INSERTWEBURLHERE/api/bankaccounts?id=${processor_id}`;
 fetch(url)
 .then(response => response.json())
 .then((data) => {
  bapSelect.innerHTML = ""; // clear second dropdown
  data.forEach((bap) => { // go through all the BAPs
  const elem = `<option value="${bap.id}">${bap.bank_name}</option>`; // create option elements to insert into the second dropdown, bank_name is the chosen label method in the form
  bapSelect.insertAdjacentHTML("beforeend", elem); // insert options into the dropdown
  });
 });
}

4) Trigger the JS when the first dropdown field is changed:

processor.addEventListener('change', function () {
 update_baps(parseInt(processor.value));
});

John Baker · Accepted Answer · 2018-09-18 15:12:06Z

0

You should add an id to the selects so you can identify them form the script.

$('select#processor').on('change', function() {
      var processor_id = this.value;
      var processor_bank_account = $('select#processor_bank_account')

      $.ajax({
        type: "GET", 
        url: <%= your_path %> ,
        data: { processor_id: processor_id },
        success: function(data, textStatus, jqXHR){
          processor_bank_account.empty();
          var option = new Option(data.bank_name, data.id, false, false);
          processor_bank_account.append(option);
        },
        error: function(jqXHR, textStatus, errorThrown){...}
      })
 });

answered Sep 18, 2018 at 15:12

John Baker

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