Pass data to getChildHtml() or call method on child block

Question

I want to be able to pass data to the getChildHtml() call. The reason is, the output of the block is dependant upon a product type. So i want to pass the product to the getChildHtml so that it can decide on the output.

I am doing this inside template/checkout/cart/item/default.phtml.

Ideally, the call would look like:

echo $this->getChildHtml('child_block_name', $_item);

Then my block can get the product type from the item and display the correct output.

Since it is definitely not possible to pass this data to getChildHtml - how else can this type of behaviour be achieved without having to rewrite the core block

The two solutions i currently have are as follows (neither very attractive):

1 - Create a helper and access the html output via the helper instead of letting a block and template render it ala $this->helper('my_module')->getItemHtml($_item);

2 - Access the child block and setData on it inside the template:

 $this->getChild('child_name')->setData('item', $_item);
 echo $this->getChildHtml('child_name')

I think in terms of the Magento architecture, number 2 is the lesser of two evils, but it is darn ugly looking inside a template.

Answer 1

You can add a method on the parent block to fetch the child depending on the product type (I've seen this kind of logic a couple of times in core or something similar):

class ParentBlock 
{
    public function getIntuitiveNameChild($item)
    {
        return $this->getChild("intuitive_child")
                    ->setProductType($item->getProductType()) 
                    // You can also decide the product type in this setter, in the Child block.
                    ->setItem($item);
    }

    public function getIntuitiveNameChildDinamically($item)
    {
        return $this->getChild("intuitive_child_" . $item->getProductType())
                    ->setItem($item); 
    }    
}

// parent tpl
// i suggest you avoid getChildHtml(), unless you're certain that methods won't need to be called from the tpl
echo $this->getIntuitiveNameChild($_item)
          // ->someOtherMethod()
          ->toHtml();

Still, seeing how you modify the layout xml to add children blocks, you may be interested in how Magento decided to work with rendering markup depending on product types in Mage_Sales_Block_Items_Abstract::getItemHtml() and Mage_Checkout_Block_Cart_Abstract::getItemHtml().

Answer 2

The above solution wont work if you are displaying child block in foreach loop.

For that you need to use following code:

<?php
foreach ($blocks as $block) {
    $this->getChild("child.block")->setData("my_data", $any_data);
    echo $this->getChildHtml('child.block', false);
}
?>

In child.block you can use $this->getMyData() to get the data. Using this strategy the child block will always get the latest data from parent.

The second parameter of getChildHtml() is $useCache. Setting it to false prevents the first output to be cached and forces rendering the child again.

Answer 3

A block that can receive data is called a widget; though this can be done via multiple block definitions (based on the properties of $_item).

Magento does something very similar in the core by loading the payment method block based on the method's short code:

<dd>
    <?php echo $this->getChildHtml('payment.method.'.$_code) ?>
</dd>

You could do the same with this pseudo-code:

if($type = $_item->getTypeId()){
    $this->getChildHtml('my.block.' . $type);
}

All that would require would be to have a different block type for each product type - bundle, simple, configurable, virtual, grouped. Not so bad, really.

If you really want to use a widget - it would be something to the effect of your second idea in your edited question:

<?php
echo $this->getLayout()->createBlock('yourcompany/widget_class')->setType($_item->getTypeId())->toHtml();

Creating a widget probably outside of the scope of this answer - but it's not terribly difficult, and has the advantage of being able to be repurposed for CMS blocks, though for your use case I don't think that is applicable.

For more information on creating a widget:

http://www.magentocommerce.com/knowledge-base/entry/tutorial-creating-a-magento-widget-part-1

Answer 4

For Magento 2, you can use

<?php
foreach ($blocks as $block) {
    $block->getChildBlock("child.block")->setData("my_data", $any_data);
    echo $block->getChildHtml('child.block', false);
}
?>

To get the data,

$block->getMyData();