RondoForm

Handle dynamic nested forms, same as Cocoon, but using StimulusJS

Install the gem and add to the application's Gemfile by executing:

$ bundle add rondo_form

Or inside the Gemfile add the following

$ gem 'rondo_form', '~> 1.0'

Run the installation task:

$ rails g rondo_form:install

For example, you have Project model, which has has_many relationship with Task model:

rails g scaffold Project name:string description:string
rails g model Task description:string done:boolean project:belongs_to

You need to add accepts_nested_attributes_for to Project model:

class Project < ApplicationRecord
  has_many :tasks, dependent: :destroy
  accepts_nested_attributes_for :tasks, reject_if: :all_blank, allow_destroy: true
end

The RondoForm gem adds two helper functions: link_to_add_association and link_to_remove_association. More details about two view helpers here.

The example below illustrates the way to use it.

In your projects/_form partial:

<%= simple_form_for(@project) do |f| %>

  <div class="form-inputs">
    <%= f.input :name %>
    <%= f.input :description %>
  </div>

  <h3 class="text-xl mt-4">Tasks</h3>
  <div class="my-2" data-controller="nested-rondo" data-nested-rondo-field-class-value="task-field">
    <div data-nested-rondo-target="fieldContain">
      <%= f.simple_fields_for :tasks do |task| %>
        <%= render "task_fields", f: task %>
      <% end %>
    </div>
    <div class="links">
      <%= link_to_add_association "Add Task", f, :tasks %>
    </div>
  </div>

  <div class="form-actions mt-4">
    <%= f.button :submit %>
  </div>
<% end %>

In your _task_fields partial:

<div class="task-field">
  <%= f.input :description %>
  <%= f.input :done, as: :boolean %>
  <%= link_to_remove_association "Remove Task", f %>
</div>

Using projects example, in your controller ProjectsController, your params method should look like:

def project_params
  params.require(:project).permit(:name, :description, tasks_attributes: [:description, :done, :_destroy, :id])
end

params :_destroy allow to delete tasks and :id allow to update tasks on update action

View details implement for manual Rails form at this PR dynamic nested form with rondo_form

link_to_add_association(name, form_builder, render_options, html_options)
# Link text is passed in as name

link_to_add_association(form_builder, render_options, html_options, &block)
# Link text is passed in as a block

• render_options: hash containing options for Rails' render helper - This is passed to the Rails render helper to provide the options that are desired when rendering your association fields. If no special requirements are needed, can be passed as nil or and empty hash {}.

• html_options: hash containing options for Rails' link_to helper - This is passed to the Rails link_to helper to provide the options that are desired when rendering your association fields. If no special requirements are needed, can be passed as nil or and empty hash {}.

link_to_remove_association(name, form_builder, html_options)
# Link text is passed in as name

link_to_remove_association(form_builder, html_options, &block)
# Link text is passed in as a block

• html_options: hash containing options for Rails' link_to helper - This is passed to the Rails link_to helper to provide the options that are desired when rendering your association fields. If no special requirements are needed, can be passed as nil or and empty hash {}.

• I named Stimulus controller nested-rondo, feel free to change the name of data-controller to match your purpose
• data-nested-rondo-target="fieldContain" must be added to an element that wraps all nested fields, the new field will be appended to this element.
• data-nested-rondo-field-class-value is used to detect the element that needs to be removed. Its value must match the class name of an element that wraps the partial. If you do not declare it, it will default remove the closest parent element.
• The partial added when clicking link_to_add_association is named for the association name with the _fields suffix. In this example, the partial is named task_fields. You can change the partial name by passing the partial_name option to link_to_add_association.

Import Maps

• If you use importmap. it auto loads eagerly all controllers defined in the import map under controllers/**/*_controller, so you maybe don't need under code.

import NestedRondoController from "./nested_rondo_controller"
lazyLoadControllersFrom("nested-rondo", NestedRondoController)

Bug reports and pull requests are welcome on GitHub at https://github.com/hungle00/rondo_form.

The gem is available as open source under the terms of the MIT License.