How to add an extra shipping cost to the total price of my shopping cart in ruby ​on rails?

Question

Apparently everything on my page is "fine" but I would like to make the following modifications, I hope you can help me. I would like the user to select the National shipping option of the form check that I have below 1 , add +150 to the Total price of the cart and when they select Personal delivery only CDMX only the total price of the products is displayed. I had thought and even tried with an if but did not know how to implement it.

This is my shopping_cart.rb class from app / models

class ShoppingCart < ApplicationRecord
    has_many :in_shopping_carts
    has_many :products, through: :in_shopping_carts
    enum status: {payed: 1, default: 0}

    
    def total
        products.sum(:pricing)
    end
    
end

This is my show.haml class from app / views / shopping_carts

%h1.mb-3.text-align:center.text-center Mi carrito
.form-check
    %p Selecciona tu tipo de envio:
    %input#exampleRadios1.form-check-input{checked: "checked", name: "exampleRadios", type: "radio", value: "option1"}/
    %label.form-check-label{for: "exampleRadios1"}
    Entrega personal solo CDMX
.form-check
    %input#exampleRadios2.form-check-input{name: "exampleRadios", type: "radio", value: "option2"}/
    %label.form-check-label{for: "exampleRadios2"}
    Envio nacional

.card.large-padding 
    %table.table.table-striped.table-hover.small#table_shopping_cart
        %thead
            %td Producto
            %td Costo
            %td Acciones
        %tbody
            -@shopping_cart.in_shopping_carts.each do |i_sh|
                -product = i_sh.product
                %tr{id: "#{product.id}"}
                    %td= product.name
                    %td= product.pricing
                    %td= link_to "Eliminar",i_sh,method: :delete
    .top-space.large-padding.text-center#payment_form
        %p.medium
            %strong
                Total: $
                =@shopping_cart.total

And This is my shopping_carts_controller.rb class from app / controllers

class ShoppingCartsController < ApplicationController
    def show
        if @shopping_cart.payed?
            render "shopping_carts/complete"
            return
        end
    end
end
            

Answer 1

You will need to tell the controller that either option was selected.

The basic way to do this is for the user to press a button after they select the radio to submit to a controller method. This controller method will tell your shopping cart if it becomes either a National Delivery or a Personal Pickup type.

Roughly something like:

# view
form_tag change_delivery_method_path(@shopping_cart)
  label
    Personal
    radio_button_tag "delivery_method", "personal"
  label
    National
    radio_button_tag "delivery_method", "national"
  submit_button_tag

# controller
def change_delivery_method
  shopping_cart = ShoppingCart.find(params[:shopping_cart_id])
  shopping_cart.update(delivery_method: params[:delivery_method])
end

From there, you can modify the total accordingly.

class ShoppingCart < ApplicationRecord
    has_many :in_shopping_carts
    has_many :products, through: :in_shopping_carts
    enum status: {payed: 1, default: 0}
    enum delivery_method: { personal: 0, national: 1 }
    
    def total
        products.sum(:pricing) + delivery_fee
    end

    def delivery_fee
        return 150 if national?
        return 0 if personal?
    end
end

The next level would be converting the form submit into AJAX.