How to use collection select for hidden value - ruby-on-rails

Question

I have a table called sublet post which has these columns and there is a reference column to the property table.
create_table "sublet_posts", force: :cascade do |t|
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "property_id"
t.index ["property_id"], name: "index_sublet_posts_on_property_id"
Property table
create_table "properties", force: :cascade do |t|
t.string "address"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
In the sublet post form view
<div class="field">
<%= collection_select(:sublet_post, :property_id, #properties, :id, :address, prompt: true) %>
<%= form.hidden_field :property_id, value: params[:sublet_post][:property_id] %>
</div>
In the form view, I am using the address as the selections and if a user clicks on an address, I would like the id to be stored in the for the value of the hidden value :property_id. I would like to do something similar to the code above.

Answer 1

You can add an id to both elements and catch the change event.
The html will be so:
<div class="field">
<%= collection_select(:sublet_post, :property_id, #properties, :id, :address, prompt: true, id: 'the_collection') %>
<%= form.hidden_field :property_id, value: params[:sublet_post][:property_id], id: 'the_field'%>
</div>
And the javascript, if you are using jQuery :
$(document).on('change', '#the_collection', function(event) {
var element = $(event.target);
element.siblings('#the_field').val(element.val());
});
https://api.jquery.com/siblings/