Call <update> handler from within <block>

Question

I'm still pretty new to Magento (1.9 EE) so some of my terminology may be incorrect, apologies if so.

Anyway, in one of my layout XML files, I have a custom block which I can include using the update tag, something like

<custom_block>
    <block name="...">
        ...
    </block>
</custom_block>

<another_block_1>
    <update handle="custom_block" />
</another_block_1>

This all works fine. However, when I try to call the update from within a block tag, it doesn't work, something like:

<another_block_2>
    <block name="sub_another_block_2" ...>
        <update handle="custom_block" />
    </block>
</another_block_2>

Is what I'm trying to do possible? A colleague mentioned that update might not be the correct tag.

Answer 1

The only meaningful occurrence o update and handle I found is in the Layout update class.
What this method does, is to parse the merged layout handle and if it finds child nodes with the name update and the attribute handle it merges that handle to the current handle.
As you can see it only looks for update nodes as direct child nodes of the main handle tag. It does not look for it inside the blocks or any other tags you might have.
In conclusion, no, adding update handles inside blocks does not work.