Custom module block - how to include sub-template?

Question

I've created a basic module that has a block (extending Mage_Catalog_Block_Product_List). The purpose of the module is list products of a certain attribute set, and allow the user to filter them by defined attributes, in a certain way.

I have the module/block working, being called from a CMS page as follows:
{{block type="abc_pdn/list" name="pdn" template="catalog/product/list.phtml" attribute_set_id="9" attribute_list="rel_manu,rel_make"}}

This works fine, and allows me to list products using the default Magento template. The bit I'm struggling with is to inject a custom block above the product list that contains 2 dropdowns, one for each of the attributes. I have some code written that will output dropdowns as HTML, but I'm not sure how I add these through the template.

What is the Magento way of adding another block template within my module containing my custom dropdown HTML code?

Answer 1

Here is an idea.
Set a custom template for your block instead of catalog/product/list.phtml. Let's call it: abc/pdn/list.phtml.
Now in your block class add a new method that will retrieve the product list block:

public function getProductsBlock(){
    if (!$this->hasData('products_block')){ //cache in variable
        $productsBlock = Mage::app()->getLayout()->createBlock('catalog/product_list')
                ->setAttributeSetId($this->getAttributeSetId()) //pass the attribute set to the product list
                ->setTemplate('catalog/product/list.phtml');//set the template
        $this->setData('products_block', $productsBlock);
    }
    return $this->getData('products_block');
}

In your new template abc/pdn/list.phtml do something like this:

<div class="attribute_list">
    <!-- list here your attribute dropdowns -->
</div>
<?php echo $this->getProductsBlock()->toHtml(); ?><!-- list the products -->

Answer 2

If you use the update layout text area of the CMS page this would be easy.

<reference name="content">
   <block type="abc_pdn/list" name="pdn" template="catalog/product/list.phtml" attribute_set_id="9" attribute_list="rel_manu,rel_make">
      <block "your/custom_block" name="custom_block" as="custom_block" template="your/custom/template.phtml"/>
   </block>
</reference>

Now in the catalog/product/list.phtml you can call it using

echo $this->getChildHtml('custom_block');