app/controllers/tables_arrangements_controller.rb

@@ -6,10 +6,15 @@ class TablesArrangementsController < ApplicationController
   end
 
   def show
-    Seat.joins(:guest).where(tables_arrangement_id: params[:id])
-        .pluck(:table_number, Arel.sql("guests.first_name || ' ' || guests.last_name "), 'guests.id')
+    Seat.joins(guest: :group)
+        .where(tables_arrangement_id: params[:id])
+        .pluck(
+          :table_number,
+          Arel.sql("guests.first_name || ' ' || guests.last_name "), 'guests.id',
+          'groups.color'
+        )
         .group_by(&:first)
-        .transform_values { |table| table.map { |(_, name, id)| { id:, name: } } }
+        .transform_values { |table| table.map { |(_, name, id, color)| { id:, name:, color: } } }
         .map { |number, guests| { number:, guests: } }
         .then { |result| render json: result }
   end

app/models/group.rb

@@ -7,7 +7,15 @@ class Group < ApplicationRecord
   has_many :children, class_name: 'Group', foreign_key: 'parent_id'
   belongs_to :parent, class_name: 'Group', optional: true
 
+  before_create :set_color
+
   scope :roots, -> { where(parent_id: nil) }
 
   has_many :guests
+
+  private
+
+  def set_color
+    self.color = "##{SecureRandom.hex(3)}"
+  end
 end

db/migrate/20241103133122_add_color_to_group.rb

@@ -0,0 +1,5 @@
+class AddColorToGroup < ActiveRecord::Migration[7.2]
+  def change
+    add_column :groups, :color, :string
+  end
+end

db/schema.rb

@@ -1,5 +1,3 @@
-# Copyright (C) 2024 Manuel Bustillo
-
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
@@ -12,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2024_11_03_093955) do
+ActiveRecord::Schema[7.2].define(version: 2024_11_03_133122) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -35,6 +33,7 @@ ActiveRecord::Schema[7.2].define(version: 2024_11_03_093955) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.uuid "parent_id"
+    t.string "color"
     t.index ["name"], name: "index_groups_on_name", unique: true
     t.index ["parent_id"], name: "index_groups_on_parent_id"
   end

spec/models/group_spec.rb

@@ -3,5 +3,9 @@
 require 'rails_helper'
 
 RSpec.describe Group, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
+  describe 'callbacks' do
+    it 'should set color before create' do
+      expect(create(:group).color).to be_present
+    end
+  end
 end