Magento 1 How to Hide Empty or Null Attribute in Compare Page

Question

I've realised there are many answer which actually are technically incorrect because they only are taking into account one product. They remove any attribute that is empty or null even if the second product's attribute is not null or empty.

So I decided to post an answer.

Answer 1

We need to override the block class Mage_Catalog_Block_Product_Compare_List and function getAttributes(), this way we have pre sorted array list of attributes instead of having to do the changes at template level.

public function getAttributes()
{
  if (is_null($this->_attributes)) {
     $this->_attributes = $this->getItems()->getComparableAttributes();
  }

  // Remove Null Attribute From Compare List
  foreach($this->_attributes as $attribute) {
     $size  = sizeof($this->getItems());
     $count = 0;

     foreach($this->getItems() as $item) {
        $itemAttribute = $item->getData($attribute->getName());
        $trimAttribute = trim($itemAttribute);
        if(is_null($itemAttribute) || empty($trimAttribute)) {
           $count++;
        }

        if($count == $size) {
           unset($this->_attributes[$attribute->getName()]);
        }
     }
  }

  return $this->_attributes;

}