<?php
class RelatedProductExtension extends DataExtension {
	private static $many_many = array(
		'RelatedProducts' => 'Product'
	);

	public function updateProductCMSFields(&$fields) {
	$gridField = GridField::create(
		'RelatedProducts',
		'Related Products',
		$this->owner->getManyManyComponents('RelatedProducts'),
		GridFieldConfig::create()
			->addComponent(new GridFieldButtonRow('before'))
			->addComponent(new GridFieldAddExistingAutocompleter('buttons-before-left'))
			->addComponent(new GridFieldDataColumns())
			->addComponent(new GridFieldSortableHeader())
			->addComponent(new GridFieldDeleteAction(true))
		);
		$fields->addFieldToTab('Root.RelatedProducts', $gridField);
	}
}