silverstripe-comments/code/admin/CommentsGridFieldAction.php

<?php

class CommentsGridFieldAction implements GridField_ColumnProvider, GridField_ActionProvider {
	/**
	 * {@inheritdoc}
	 */
	public function augmentColumns($gridField, &$columns) {
		if(!in_array('Actions', $columns)) {
			$columns[] = 'Actions';
		}
	}

	/**
	 * {@inheritdoc}
	 */
	public function getColumnAttributes($gridField, $record, $columnName) {
		return array('class' => 'col-buttons');
	}

	/**
	 * {@inheritdoc}
	 */
	public function getColumnMetadata($gridField, $columnName) {
		if($columnName == 'Actions') {
			return array('title' => '');
		}
	}

	/**
	 * {@inheritdoc}
	 */
	public function getColumnsHandled($gridField) {
		return array('Actions');
	}

	/**
	 * {@inheritdoc}
	 */
	public function getColumnContent($gridField, $record, $columnName) {
		if(!$record->canEdit()) return;

		$field = "";

		$field .= GridField_FormAction::create(
			$gridField,
			'CustomAction' . $record->ID,
			'Mark As Spam',
			'spam',
			array('RecordID' => $record->ID)
		)->Field();

		$field .= GridField_FormAction::create(
			$gridField,
			'CustomAction' . $record->ID,
			'Mark As Not Spam',
			'not_spam',
			array('RecordID' => $record->ID)
		)->Field();

		return $field;
	}

	/**
	 * {@inheritdoc}
	 */
	public function getActions($gridField) {
		return array('spam', 'not_spam');
	}

	/**
	 * {@inheritdoc}
	 */
	public function handleAction(GridField $gridField, $actionName, $arguments, $data) {
		if($actionName == 'spam') {
			$comment = Comment::get()->byID($arguments["RecordID"]);

			$comment->Moderated = true;
			$comment->IsSpam = true;
			$comment->write();

			// output a success message to the user
			Controller::curr()->getResponse()->setStatusCode(
				200,
				'Comment marked as spam.'
			);
		}

		if($actionName == 'not_spam') {
			$comment = Comment::get()->byID($arguments["RecordID"]);

			$comment->Moderated = true;
			$comment->IsSpam = false;
			$comment->write();

			// output a success message to the user
			Controller::curr()->getResponse()->setStatusCode(
				200,
				'Comment marked as not spam.'
			);
		}
	}
}