# Create custom product code generator strategy

Product code generator strategies control what product variant codes are generated.

Besides the [built-in](https://doc.ibexa.co/en/latest/product_catalog/product_catalog_configuration/#code-generation-strategy) strategies, you can create your own ones.

A code generator strategy must implement `Ibexa\Contracts\ProductCatalog\Local\CodeGenerator\CodeGeneratorInterface`.

The following example shows how to add a generator strategy that creates code, based on the product base code and an incremental index number.

First, create the generator strategy class:

```
<?php

declare(strict_types=1);

namespace App\CodeGenerator\Strategy;

use Ibexa\Contracts\Core\Exception\InvalidArgumentException;
use Ibexa\Contracts\ProductCatalog\Local\CodeGenerator\CodeGeneratorContext;
use Ibexa\Contracts\ProductCatalog\Local\CodeGenerator\CodeGeneratorInterface;

final class CustomIncrementalCodeGenerator implements CodeGeneratorInterface
{
    public function generateCode(CodeGeneratorContext $context): string
    {
        if (!$context->hasBaseProduct()) {
            throw new InvalidArgumentException('$context', 'missing base product');
        }

        if (!$context->hasIndex()) {
            throw new InvalidArgumentException('$context', 'missing index');
        }

        return $context->getBaseProduct()->getCode() . 'v' . $context->getIndex();
    }
}
```

This generator uses the provided context to get product information (in this case the code of the base product) and the incremental number.

Then, register the strategy generator as a service and tag it with `ibexa.product_catalog.code_generator`:

```
services:
    App\CodeGenerator\Strategy\CustomIncrementalCodeGenerator:
        tags:
            - { name: 'ibexa.product_catalog.code_generator', type: 'custom_incremental' }
```

Use the defined `type` in [catalog configuration](https://doc.ibexa.co/en/latest/product_catalog/product_catalog_configuration/#code-generation-strategy) to apply codes generated by this strategy to new product variants.