trying to implement retrieve attachments on update action - ruby-on-rails

Question

I'm following the Andy Leverenz's (WebCrunch) Dropzone/Stimulus tutorial and don't know how to implement the update action. I can upload multiple files with ease but when I try to edit it, all my attachments disappear and I have to re-upload. I think that what I need to do is fetch my object attachments on stimulus controller (#rails/ujs) and check if browser URL match with edit_path, then append files on the form when it loads (document.ready).
dropzone_controller.js
import Dropzone from "dropzone";
import { Controller } from "stimulus";
import { DirectUpload } from "#rails/activestorage";
import {
getMetaValue,
toArray,
findElement,
removeElement,
insertAfter
} from "helpers";
export default class extends Controller {
static targets = ["input"];
connect() {
this.dropZone = createDropZone(this);
this.hideFileInput();
this.bindEvents();
Dropzone.autoDiscover = false;
}
// Private
hideFileInput() {
this.inputTarget.disabled = true;
this.inputTarget.style.display = "none";
}
bindEvents() {
this.dropZone.on("addedfile", file => {
setTimeout(() => {
file.accepted && createDirectUploadController(this, file).start();
}, 500);
});
this.dropZone.on("removedfile", file => {
file.controller && removeElement(file.controller.hiddenInput);
});
this.dropZone.on("canceled", file => {
file.controller && file.controller.xhr.abort();
});
}
get headers() {
return { "X-CSRF-Token": getMetaValue("csrf-token") };
}
get url() {
return this.inputTarget.getAttribute("data-direct-upload-url");
}
get maxFiles() {
return this.data.get("maxFiles") || 1;
}
get maxFileSize() {
return this.data.get("maxFileSize") || 256;
}
get acceptedFiles() {
return this.data.get("acceptedFiles");
}
get addRemoveLinks() {
return this.data.get("addRemoveLinks") || true;
}
}
class DirectUploadController {
constructor(source, file) {
this.directUpload = createDirectUpload(file, source.url, this);
this.source = source;
this.file = file;
}
start() {
this.file.controller = this;
this.hiddenInput = this.createHiddenInput();
this.directUpload.create((error, attributes) => {
if (error) {
removeElement(this.hiddenInput);
this.emitDropzoneError(error);
} else {
this.hiddenInput.value = attributes.signed_id;
this.emitDropzoneSuccess();
}
});
}
createHiddenInput() {
const input = document.createElement("input");
input.type = "hidden";
input.name = this.source.inputTarget.name;
insertAfter(input, this.source.inputTarget);
return input;
}
directUploadWillStoreFileWithXHR(xhr) {
this.bindProgressEvent(xhr);
this.emitDropzoneUploading();
}
bindProgressEvent(xhr) {
this.xhr = xhr;
this.xhr.upload.addEventListener("progress", event =>
this.uploadRequestDidProgress(event)
);
}
uploadRequestDidProgress(event) {
const element = this.source.element;
const progress = (event.loaded / event.total) * 100;
findElement(
this.file.previewTemplate,
".dz-upload"
).style.width = `${progress}%`;
}
emitDropzoneUploading() {
this.file.status = Dropzone.UPLOADING;
this.source.dropZone.emit("processing", this.file);
}
emitDropzoneError(error) {
this.file.status = Dropzone.ERROR;
this.source.dropZone.emit("error", this.file, error);
this.source.dropZone.emit("complete", this.file);
}
emitDropzoneSuccess() {
this.file.status = Dropzone.SUCCESS;
this.source.dropZone.emit("success", this.file);
this.source.dropZone.emit("complete", this.file);
}
}
function createDirectUploadController(source, file) {
return new DirectUploadController(source, file);
}
function createDirectUpload(file, url, controller) {
return new DirectUpload(file, url, controller);
}
function createDropZone(controller) {
return new Dropzone(controller.element, {
url: controller.url,
headers: controller.headers,
maxFiles: controller.maxFiles,
maxFilesize: controller.maxFileSize,
acceptedFiles: controller.acceptedFiles,
addRemoveLinks: controller.addRemoveLinks,
autoQueue: false
});
}
index.js
// Load all the controllers within this directory and all subdirectories.
// Controller files must be named *_controller.js.
import { Application } from "stimulus";
import { definitionsFromContext } from "stimulus/webpack-helpers";
const application = Application.start();
const context = require.context("controllers", true, /_controller\.js$/);
application.load(definitionsFromContext(context));
_form.html.erb
<%= form_for #ad, :html => { :multipart => true } do |form| %>
<% if ad.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(ad.errors.count, "error") %> prohibited this ad from being saved:</h2>
<ul>
<% ad.errors.each do |error| %>
<li><%= error.full_message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="form-group">
<%= form.label :title %>
<%= form.text_field :title, class: 'form-control' %>
</div>
<div class="form-group">
<%= form.label :description %>
<%= form.text_area :description, class: 'form-control' %>
</div>
<div class="form-group">
<%= form.label :images %>
<div class='dropzone dropzone-default dz-clickable' data-controller='dropzone' data-max-filesize='2'
data-dropzone-max-files='4'>
<%= form.file_field :images, multiple: true, direct_upload: true, data: { target: 'dropzone.input' } %>
<div class='dropzone-msg dz-message needsclick'>
<h3 class='dropzone-msg-title'>Drag here to upload or click here to browse</h3>
<span class='dropzone-msg-desc'>2 MB file size maximum. Allow file types png, jpg.</span>
</div>
</div>
</div>
<div class="form-group">
<%= form.submit class: 'btn btn-primary mb-2' %>
</div>
<% end %>