Getting started with Order Adjuster plugin

Question

Starting with the Business Logic plugin from https://github.com/lindseydiloreto/craft-businesslogic I'm following 3 for 2 etc with Craft Commerce to get started.

I have my main plugin file containing:

<?php
namespace Craft;
require_once('Adjusters/BusinessLogic_TaxRemover.php');

class BusinessLogicPlugin extends BasePlugin
{

    public function getName()
    {
        return 'BusinessLogic';
    }

    public function getDescription()
    {
        return '';
    }

    public function getVersion()
    {
        return '1.0.0';
    }

    public function getDeveloper()
    {
        return craft()->getSiteName();
    }

    public function getDeveloperUrl()
    {
        return '';
    }

    public function init()
    {
    }

    public function commerce_registerOrderAdjusters(){

        return [

            new Commerce_TaxAdjuster

        ];
    }

}

And within Adjusters/BusinessLogic_TaxRemover.php I have:

<?php

namespace Commerce\Adjusters;
use Craft\Commerce_LineItemModel;
use Craft\Commerce_OrderAdjustmentModel;
use Craft\Commerce_OrderModel;

class BusinessLogic_TaxRemover implements Commerce_AdjusterInterface {

    public function adjust(Commerce_OrderModel &$order, array $lineItems = []){

        $myAdjuster = new Commerce_OrderAdjustmentModel();

        $order->baseDiscount = $order->baseDiscount - 5;

        $myAdjuster->type = "Test";
        $myAdjuster->name = "Test Adjuster";
        $myAdjuster->description = "Takes $5 off the order";
        $myAdjuster->amount = -5.0;
        $myAdjuster->orderId = $order->id;

        //if your Adjuster affects lineItems rather than the total, you record the ids here
        $myAdjuster->optionsJson = ['lineItemsAffected'=>null];
        $myAdjuster->included = false;

        return [$myAdjuster];

    }

}

But whenever doing anything to the cart, I just get the error:

Error

Class 'Craft\BusinessLogic_TaxRemover' not found

C:\Users\clive\Desktop\repos\_craft\craft\plugins\businesslogic\BusinessLogicPlugin.php(38)

26     }
27 
28     public function getDeveloperUrl()
29     {
30         return '';
31     }
32 
33     public function init()
34     {
35     }
36     public function commerce_registerOrderAdjusters(){
37            return [
38             new BusinessLogic_TaxRemover
39             
40            ];
41     }
42 
43 }

Answer 1

To get an adjuster working, it's really all about consistent naming and making sure PHP can find the class. Here are the main things to address:

Your adjuster should be defined in a file that matches it's classname

So in this case a folder off the main plugin folder:

 /craft/plugins/businesslogic/Adjusters/BusinessLogic_TaxRemover.php

Include the Adjuster class file.

You can do this (at least) two ways:

include or require the adjuster file in your main plugin class

e.g.

<?php
namespace Craft;

require_once('Adjusters/BusinessLogic_TaxRemover.php');

OR you can use Craft::import (which is probably the better way I guess?)

Craft::import('plugins.businesslogic.adjusters.BusinessLogic_TaxRemover');

** The Classname must match the filename **

So e.g. in this case

<?php

namespace Commerce\Adjusters;
use Craft\Commerce_LineItemModel;
use Craft\Commerce_OrderAdjustmentModel;
use Craft\Commerce_OrderModel;

class BusinessLogic_TaxRemover implements Commerce_AdjusterInterface {

   etc
}

You must also finally register your Adjuster with commerce

And again you must use the same classname (and be mindful of namespaces!)
So in this example:

public function commerce_registerOrderAdjusters(){
    return [
        new \Commerce\Adjusters\BusinessLogic_TaxRemover

    ];
}

Answer 2

From your code examples, I believe the issue if you have a file named adjusters/BusinessLogicAdjusters.php, but the class name for that file is BusinessLogic_TaxRemover.