Layout - Pass variables from parent to child

Question

How can I access variables defined in the parent template inside a child template?

Example -> I added a new block with name product.info.grouped.news_flag as child of the block with name product.info.grouped in the catalog.xml layout of my design:

<PRODUCT_TYPE_grouped translate="label" module="catalog">
    <label>Catalog Product View (Grouped)</label>
    <reference name="product.info">
        <block type="catalog/product_view_type_grouped" name="product.info.grouped" as="product_type_data" template="catalog/product/view/type/grouped.phtml">
            <block type="core/text_list" name="product.info.grouped.extra" as="product_type_data_extra" translate="label">
                <label>Product Extra Info</label>
            </block>

            <!-- My new block -->
            <block type="core/template"
                   name="product.info.grouped.news_flag"
                   as="product_type_data_news_flag"
                   template="catalog/product/view/type/news_flag.phtml"/>

        </block>
    </reference>
</PRODUCT_TYPE_grouped>

This is the part in the template file of the parent block where I call my new block with name product.info.grouped.news_flag:

catalog/product/view/type/grouped.phtml

<?php 
    $testVar = 123;
    echo $this->getChildHtml('product_type_data_news_flag');
?>

As you can see I created a variable named $testVar with value 123.

But If I try to call the value in the child block product_type_data_news_flag then I get null:

catalog/product/view/type/news_flag.phtml

<?php
    $a = $testVar;
    echo $a; // returns null

How can I pass a variable from the parent block/template to the child block/template?

Answer 1

I see at least two possibilities :

1) In the parent block, set your data with some $this->setMyVariable('my_value') or using layout xml declaration. Then, in your child block, you should get the value with some $this->getParentBlock()->getMyVariable()

2) Or you can use the method used here

Answer 2

Alternatively, you can use Mage::register('some_var', $someVar) on parent block and Mage::registry('some_var') on child block to get the value. But in general, Julien's answer suits better.

Answer 3

I found a way. I changed the type of the child block class to the same type as the parent block.

<PRODUCT_TYPE_grouped translate="label" module="catalog">
    <label>Catalog Product View (Grouped)</label>
    <reference name="product.info">
        <block type="catalog/product_view_type_grouped" name="product.info.grouped" as="product_type_data" template="catalog/product/view/type/grouped.phtml">
            <block type="core/text_list" name="product.info.grouped.extra" as="product_type_data_extra" translate="label">
                <label>Product Extra Info</label>
            </block>

            <!-- My new block -->
            <block type="catalog/product_view_type_grouped"
                   name="product.info.grouped.news_flag"
                   as="product_type_data_news_flag"
                   template="catalog/product/view/type/news_flag.phtml"/>

        </block>
    </reference>
</PRODUCT_TYPE_grouped>

Now I can override the block class and define my variables there so I can use it in all childs.