Filtering admin grid when using observer-inserted custom column

Question

I have a custom column in my catalog product grid for a custom attribute. I'm using the observer method of inserting the column: on core_block_abstract_prepare_layout_before:

public function appendAuthorColumn(Varien_Event_Observer $observer)
{
 $block = $observer->getBlock();
 if ($block->getType() == 'adminhtml/catalog_product_grid') {
 $authors = Mage::helper('companyx_authors')->getAuthorOptionHash();
 $block->addColumnAfter('author_id', array(
 'header' => 'Author',
 'type' => 'options',
 'index' => 'author_id',
 'options' => $authors,
 'width' => '150',
 ), 'name');
 }
}

I am updating the collection using the catalog_product_collection_load_before event:

public function addAuthorToCollection(Varien_Event_Observer $observer)
{
 $collection = $observer->getCollection();
 if (!isset($collection)) {
 return $this;
 }
 $collection->addAttributeToSelect('author_id');
 return $this;
}

Everything works as expected, except when I want to filter by product name: the author column is blank. When I filter by any other column, it is populated.

The only difference with product name is that it's a free text field. I can't think of anything else.

Answer 1

Instead of adding the attribute to the collection, join it:

public function addAuthorToCollection(Varien_Event_Observer $observer)
{
 $collection = $observer->getCollection();
 if (!isset($collection)) {
 return $this;
 }
 $collection->joinAttribute('author_id', 'catalog_product/author_id', 'entity_id', null, 'left'); //use this instead
 return $this;
}