Create a record with a multiselect through a many-to-many relationship

Context: In this case, a card has many expense categories through a many to many relationships, using a join table (card expense categories). We want to be able to create a card, selecting the categories, and creating the card expense categories at the same time.

Implementation:

We will use a smart action form with a hook to retrieve the categories as values for the multi select.

Then we implement the creation of cards and expenseCategories in the form.

forest/cards.js

const { collection } = require('forest-express-sequelize');
const { expenseCategories } = require('../models');

// This file allows you to add to your Forest UI:
// - Smart actions: <https://docs.forestadmin.com/documentation/reference-guide/actions/create-and-manage-smart-actions>
// - Smart fields: <https://docs.forestadmin.com/documentation/reference-guide/fields/create-and-manage-smart-fields>
// - Smart relationships: <https://docs.forestadmin.com/documentation/reference-guide/relationships/create-a-smart-relationship>
// - Smart segments: <https://docs.forestadmin.com/documentation/reference-guide/segments/smart-segments>
collection('cards', {
  actions: [
    {
      name: 'Create card',
      type: 'global',
      fields: [
        {
          field: 'name',
          type: 'String',
          isRequired: true,
        },
        {
          field: 'user',
          type: 'Number',
          reference: 'users.id',
          isRequired: true,
        },
        {
          field: 'categories',
          type: ['Enum'],
        },
      ],
      hooks: {
        load: async ({ fields, request }) => {
          const categories = fields.find(
            (field) => field.field === 'categories'
          );
          categories.enums = await expenseCategories
            .findAll({ raw: true })
            .map((category) => category.title);
          return fields;
        },
      },
    },
  ],
  fields: [],
  segments: [],
});

routes/cards.js

const express = require('express');
const { PermissionMiddlewareCreator } = require('forest-express-sequelize');
const {
  cards,
  cardExpenseCategories,
  expenseCategories,
} = require('../models');

const router = express.Router();
const permissionMiddlewareCreator = new PermissionMiddlewareCreator('cards');

// This file contains the logic of every route in Forest for the collection cards:
// - Native routes are already generated but can be extended/overridden - Learn how to extend a route here: <https://docs.forestadmin.com/documentation/v/v6/reference-guide/routes/extend-a-route>
// - Smart action routes will need to be added as you create new Smart Actions - Learn how to create a Smart Action here: <https://docs.forestadmin.com/documentation/v/v6/reference-guide/actions/create-and-manage-smart-actions>

//...

//Smart action - Create a card
router.post(
  '/actions/create-card',
  permissionMiddlewareCreator.smartAction(),
  (req, res) => {
    let attrs = req.body.data.attributes.values;
    categories_attrs = attrs['categories'];
    attrs = { name: attrs['name'], userId: attrs['user'] };

    return cards
      .create(attrs)
      .then((card) => {
        categories_attrs.forEach((category) => {
          return expenseCategories
            .findOne({ where: { title: category } })
            .then((expenseCategory) =>
              cardExpenseCategories.create({
                cardId: card.id,
                expenseCategoryId: expenseCategory.id,
              })
            );
        });
      })
      .then(() => {
        res.send({
          success: 'Your card is created!',
          refresh: { relationships: ['cardExpensesCategories'] },
        });
      });
  }
);

Rails version:

lib/forest_liana/collections/card.rb

class Forest::Card
    include ForestLiana::Collection
    collection :Card

    action 'Create Card',
        type: 'global',
        fields: [{
            field: "name",
            type: "String",
            isRequired: true,
        },
        {
            field: "user",
            type: "Number",
            reference: "User.id",
            isRequired: true,
        },
        {
            field: "company",
            type: "Number",
            reference: "Company.id",
            isRequired: true,
        },
        {
            field: "vendor",
            type: "Number",
            reference: "Vendor.id",
            isRequired: true,
        },
        {
            field: "categories",
            type: ['Enum'],
        }
        ],
        :hooks => {
            :load => -> (context) {
                categories = context[:fields].find{|field| field[:field] == 'categories'}
                categories[:enums] = ExpenseCategory.all.pluck(:title)
                return context[:fields]
            }
        }
end

config/routes.rb

Rails.application.routes.draw do
  ...
  namespace :forest do
    post '/actions/create-card' => 'cards#create_card'
  end
  mount ForestLiana::Engine => '/forest'
end

controllers/forest/cards_controller.rb

class Forest::CardsController < ForestLiana::SmartActionsController
    def create_card
        attrs = params.dig('data', 'attributes', 'values')
        categories_attrs = attrs['categories'];
        attrs = { name: attrs['name'], user_id: attrs['user'], company_id: attrs['company'], vendor_id: attrs['vendor'] };

        card = Card.create(attrs)
        categories_attrs.each do|category|
            expense_category = ExpenseCategory.find_by(title: category)
            card_expense_category = CardExpenseCategory.create(card_id: card.id, expense_category_id: expense_category.id)
        end

        render json: { success: 'Your card has been created.' }
    end
end