app/controllers/expenses_controller.rb

@@ -8,4 +8,15 @@ class ExpensesController < ApplicationController
   def index
     render json: Expense.all.order(pricing_type: :asc, amount: :desc).as_json(only: %i[id name amount pricing_type])
   end
+
+  def update
+    Expense.find(params[:id]).update!(expense_params)
+    render json: {}, status: :ok
+  end
+
+  private
+
+  def expense_params
+    params.require(:expense).permit(:name, :amount, :pricing_type)
+  end
 end

config/routes.rb

@@ -2,7 +2,7 @@
 
 Rails.application.routes.draw do
   resources :groups, only: :index
-  resources :guests do
+  resources :guests, only: %i[index update] do
     post :bulk_update, on: :collection
   end
   resources :expenses, only: %i[index update] do