A Server-Side Calculated Field For Laravel Nova

Note from Qskousen:

I've just updated this package to work for Nova 4, all the credit still belongs to codebykyle for their original work here: https://github.com/codebykyle/calculated-field

Changes:

Removed dependency on outdated numeral package. Instead, it will format using Intl.NumberFormat.

In light of that, the ->numberFormat() function signature has changed to ->numberFormat($format, $locale = 'en-US'), where $format is a valid format JSON string from Intl.NumberFormat (link above), for example, ->numberFormat("{style: 'currency', currency: 'usd'}"). In this instance, the locale is left to default of en-US.

The formatting only works in some specific scenarios. Doesn't work very well except on a readonly listener field. I don't think this was fully implemented in codebykyle's version, which is probably why it wasn't in the readme. Results may vary.

Original readme follows

This package contains two Nova fields required to do server-side calculations from the Nova client. The user can optionally override the calculated value on the form.

For a detailed write-up of the how-and-why of this field, please visit:

https://codebykyle.com/blog/laravel-nova-custom-calculated-field

Installation

Install the package via composer:

composer require codebykyle/calculated-field

Example

For example:

As a number

As a string:

Default

The Listener field will by default sum all numbers passed to it

Usage

<?php

use Codebykyle\CalculatedField\BroadcasterField;
use Codebykyle\CalculatedField\ListenerField;

class MyResource extends Resource
{
    public function fields(Request $request) {
        return [    
            BroadcasterField::make('Sub Total', 'sub_total'),
            BroadcasterField::make('Tax', 'tax'),
            ListenerField::make('Total Field', 'total_field')
        ];
    }
}

Overriding the Callback

<?php
use Codebykyle\CalculatedField\BroadcasterField;
use Codebykyle\CalculatedField\ListenerField;

class MyResource extends Resource
{
    public function fields(Request $request) {
        return [    
            BroadcasterField::make('Sub Total', 'sub_total'),
            BroadcasterField::make('Tax', 'tax'),

            ListenerField::make('Total Field', 'total_field')
                ->calculateWith(function (Collection $values) {
                    $subtotal = $values->get('sub_total');
                    $tax = $values->get('tax');
                    return $subtotal + $tax;
                }),
        ];
    }
}

String Fields

<?php
use Codebykyle\CalculatedField\BroadcasterField;
use Codebykyle\CalculatedField\ListenerField;

class MyResource extends Resource
{
    public function fields(Request $request) {
        return [    
            BroadcasterField::make('First Name', 'first_name')
                ->setType('string'),

            BroadcasterField::make('Last Name', 'last_name')
                ->setType('string'),

            ListenerField::make('Full Name', 'full_name')
                ->calculateWith(function (Collection $values) {
                    return $values->values()->join(' ');
                }),
        ];
    }
}

Multiple Calculated Fields

<?php
use Codebykyle\CalculatedField\BroadcasterField;
use Codebykyle\CalculatedField\ListenerField;

class MyResource extends Resource
{
    public function fields(Request $request) {
        return [    
            BroadcasterField::make('Sub Total', 'sub_total')
                ->broadcastTo('total'),

            BroadcasterField::make('Tax', 'tax')
                ->broadcastTo('total'),

            ListenerField::make('Total Field', 'total_field')
                ->listensTo('total')
                ->calculateWith(function (Collection $values) {
                    $subtotal = $values->get('sub_total');
                    $tax = $values->get('tax');
                    return $subtotal + $tax;
                }),


            BroadcasterField::make('Senior Discount', 'senior_discount')
                ->broadcastTo('discount'),
    
            BroadcasterField::make('Coupon Discount', 'coupon_amount')
                ->broadcastTo('discount'),
    
            ListenerField::make('Total Discount', 'total_discount')
                ->listensTo('discount')
                ->calculateWith(function (Collection $values) {
                    $seniorDiscount = $values->get('senior_discount');
                    $couponAmount = $values->get('coupon_amount');
    
                    return $seniorDiscount + $couponAmount;
                })
        ];
    }
}