silverstripe-comments/code/model/CommentList.php

<?php

/**
 * Handles polymorphic relation for commentlist
 *
 * Uses elements of PolymorphicHasManyList in 3.2
 *
 * @author dmooyman
 */
class CommentList extends HasManyList
{

    /**
     * Retrieve the name of the class this relation is filtered by
     *
     * @return string
     */
    public function getForeignClass()
    {
        return $this->dataQuery->getQueryParam('Foreign.Class');
    }

    public function __construct($parentClassName)
    {
        parent::__construct('Comment', 'ParentID');


        // Ensure underlying DataQuery globally references the class filter
        $this->dataQuery->setQueryParam('Foreign.Class', $parentClassName);

        // For queries with multiple foreign IDs (such as that generated by
        // DataList::relation) the filter must be generalised to filter by subclasses
        $classNames = Convert::raw2sql(ClassInfo::subclassesFor($parentClassName));
        $this->dataQuery->where(sprintf(
            "\"BaseClass\" IN ('%s')", implode("', '", $classNames)
        ));
    }

    /**
     * Adds the item to this relation.
     * 
     * @param Comment $item The comment to be added
     */
    public function add($item)
    {
        // Check item given
        if (is_numeric($item)) {
            $item = Comment::get()->byID($item);
        }
        if (!($item instanceof Comment)) {
            throw new InvalidArgumentException("CommentList::add() expecting a Comment object, or ID value");
        }
        
        // Validate foreignID
        $foreignID = $this->getForeignID();
        if (!$foreignID || is_array($foreignID)) {
            throw new InvalidArgumentException("CommentList::add() can't be called until a single foreign ID is set");
        }

        $item->ParentID = $foreignID;
        $item->BaseClass = $this->getForeignClass();
        $item->write();
    }
    /**
     * Remove a Comment from this relation by clearing the foreign key. Does not actually delete the comment.
     *
     * @param Comment $item The Comment to be removed
     */
    public function remove($item)
    {
        // Check item given
        if (is_numeric($item)) {
            $item = Comment::get()->byID($item);
        }
        if (!($item instanceof Comment)) {
            throw new InvalidArgumentException("CommentList::remove() expecting a Comment object, or ID",
                E_USER_ERROR);
        }
        
        // Don't remove item with unrelated class key
        $foreignClass = $this->getForeignClass();
        $classNames = ClassInfo::subclassesFor($foreignClass);
        if (!in_array($item->BaseClass, $classNames)) {
            return;
        }
        
        // Don't remove item which doesn't belong to this list
        $foreignID = $this->getForeignID();
        if (empty($foreignID)
            || (is_array($foreignID) && in_array($item->ParentID, $foreignID))
            || $foreignID == $item->ParentID
        ) {
            $item->ParentID = null;
            $item->BaseClass = null;
            $item->write();
        }
    }
}