Extending Magento's topLinks to Include Nested/Dropdown Child Menu's - magento

Question

We've extended the Magento class Mage_Page_Block_Template_Links using the method outlined by Sonassi here.
Editing the _construct function to include our custom template:-
protected function _construct()
{
$this->setTemplate('page/template/links_nested.phtml');
}
Editing the function addLink to include $childMenu variable and allow this to be used in XML layout:-
public function addLink($label, $url = '', $title = '', $prepare = false, $urlParams = array(), $position = null, $liParams = null, $aParams = null, $beforeText = '', $afterText = '', $childMenu = false)
{
if (is_null($label) || false === $label) {
return $this;
}
$link = new Varien_Object(array(
'label' => $label,
'url' => ($prepare ? $this->getUrl($url, (is_array($urlParams) ? $urlParams : array())) : $url),
'title' => $title,
'li_params' => $this->_prepareParams($liParams),
'a_params' => $this->_prepareParams($aParams),
'before_text' => $beforeText,
'after_text' => $afterText,
'child_menu' => ($childMenu ? $this->getLayout()->getBlock($childMenu) : '')
));
$this->_links[$this->_getNewPosition($position)] = $link;
if (intval($position) > 0) {
ksort($this->_links);
}
return $this;
}
Then we wish to include <childMenu> parameter in local.xml for an item in topLinks:-
<reference name="top.links">
<action method="addLink" translate="label title before_text">
<label>Account</label>
<url />
<title>Account</title>
<prepare />
<urlParams />
<position>10</position>
<liParams>id="account-dropdown"</liParams>
<aParams />
<before_text />
<after_text />
<childMenu>account-submenu</childMenu>
</action>
</reference>
And then construct the childMenu as account-submenu:-
<reference name="top.links">
<block type="page/template_links" name="submenu" as="submenu">
<action method="setName">
<name>account-submenu</name>
</action>
<action method="addLink" translate="label title before_text">
<label>Contact Us</label>
<url />
<title>Contact Us</title>
<prepare />
<urlParams />
<position>110</position>
<liParams />
<before_text />
<after_text />
</action>
</block>
</reference>
Then we've made a few modifications to the template file to render childMenu if declared:-
<?php $_links = $this->getLinks(); ?>
<?php if(count($_links)>0): ?>
<ul class="links nav"<?php if($this->getName()): ?> id="<?php echo $this->getName() ?>"<?php endif;?>>
<?php foreach($_links as $count=>$_link): ?>
<?php if ($_link instanceof Mage_Core_Block_Abstract):?>
<?php echo $_link->toHtml() ?>
<?php else: ?>
<li<?php if($_link->getIsFirst()||$_link->getIsLast()||$count): ?> class="<?php if($_link->getIsFirst()): ?>first<?php endif; ?><?php if($_link->getIsLast()): ?> last<?php endif; ?> link-<?php echo $count ?>"<?php endif; ?> <?php echo $_link->getLiParams() ?>>
<?php echo $_link->getBeforeText() ?><a href="<?php echo $_link->getUrl() ?>" title="<?php echo $_link->getTitle() ?>" <?php echo $_link->getAParams() ?>><?php echo $_link->getLabel() ?></a><?php echo $_link->getAfterText() ?>
<?php var_dump($_link->getChildMenu()); ?>
<?php echo ($_link->getChildMenu()) ? $_link->getChildMenu()->toHtml() : ''; ?>
</li>
<?php endif;?>
<?php endforeach; ?>
</ul>
<?php endif; ?>
Everything is working as expected apart from the fact that childMenu doesn't render anything at all in the front end, so the 'My Account' top link contains no submenu.
Is there something incorrect with the call for childMenu in the template file ?
<?php echo ($_link->getChildMenu()) ? $_link->getChildMenu()->toHtml() : ''; ?>

Answer 1

In the layout XML, you should define your submenu block (<block> node) before adding it to the top links (<action method="addLink"> within <reference name="top.links">). As Magento treats the nodes as they come, he won't know that the block exists otherwise

Answer 2

To anybody having any issues with this - I thought I'd post my solution.
I don't think it's too wise to copy the core Page/Block/Template/Links.php file from app/code/core to app/code/local and making the adjustments to that file (what happens if this Links.php file is updated in a future Magento update, you'd need to ensure your override complies with the new updated file from the core).
Anyways, the issue here is definitely that the instructions are missing a step - everything makes sense right to the point where they reference (out of nowhere) the block "mymainmenu.links" - this block doesn't exist anywhere, hence it won't work. And if you keep adding your links to the "top.links" block, Magento will just keep using the default block to display your links. So the obvious answer here is to create a new block.
In your layout file add the following block (I'm using local.xml) app/design/frontend/(package)/(theme)/layout.xml
<?xml version="1.0"?>
<layout version="0.1.0">
<default>
<reference name="header"> <!-- You could also use root here to give it a larger scale access -->
<block type="templatelinks/page_template_links" name="mymainmenu.links" as="mymainmenuLinks">
<action method="setName">
<name>mymainmenu-links</name>
</action>
<action method="addLink" translate="label title">
....
</action>
</block>
</reference>
</default>
</layout>
Setting the block type to (custom module name)/(block location) instantiates our custom module and and processes our actions through that.
You'll also have to remember to display your newly created (in this instance mymainmenuLinks) block in our template(s) - In most cases it'll be your app/design/frontend/(package)/(theme)/template/page/html/header.phtml file
Locate
<?php echo $this->getChildHtml('topLinks') ?>
And replace with your new block name
<?php echo $this->getChildHtml('mymainmenuLinks') ?>