Magento 1.9 – Layout local.xml vs Module Layout

ce-1.9.0.1layout

I've recently started using the local.xml as my playground for layouts. Before I had my doubts using it because of…reasons.
I got to see it's advantages, but I hit a brick wall now.
In the default catalog.xml layout file there is a certain block (name not important). Using the layout.xml I added a generic child block to it where I want to place other blocks.

<reference name="not.important">
    <block type="core/text_list" name="extra.left.menu" as="extra" />
</reference>

So far so good.
But now, I have one extension that should add child block to the one declared above.
If I add this new block using local.xml it works nicely.

<block type="core/text_list" name="extra.left.menu" as="extra">
    <block type="myextension/some_block" template="some/template.phtml" as="some_name" name="some_name" />
</block>

But I don't want to do it via local.xml because this new extension might be disabled in the future. If I do it via local.xml and disable the extension it will flood my log files because the block does not exist anymore.
So in my extension layout file I add this:

<reference name="extra.left.menu">
    <block type="myextension/some_block" template="some/template.phtml" as="some_name" name="some_name" />
</reference>

But This way it does not work. I feel this happens because the local.xml file is loaded last, and I cannot add a module dependency so my extension layout file would be loaded after layout.xml.
How should I tackle this? Did I get something wrong?
Or if I want it like this I have to use the "good old way" of cloning catalog.xml in my theme and adding this new block in the catalog.xml of my theme?

Best Answer

When rendering the layout in Magento a few steps happen:

Handles are defined (default, catalog_product_view, etc.)
All XML files are loaded and merged to a single huge XML file, that file is stored somewhere in the cache.
The contents of all handles are loaded and merged into one page-xml file.
The order where the XML files are loaded are alphabetically and the local.xml is loaded last (there are also database layout updates which are loaded even later. (source https://github.com/OpenMage/magento-mirror/blob/magento-1.9/app/code/core/Mage/Core/Model/Layout/Update.php#L433-L438)
Finally the XML is parsed and the blocks is initiated.

So why isn't your example working? This is because the module XML file is loaded before the local.xml file. What happens is that the system first tries to add a block to a reference (to a block) which doesn't exist yet.

To solve te issue: You can use an update, updates get placed before the handles they are called in.

<default>
    <update handle="awesome_new_container_handle"/>
</default>

<awesome_new_container_handle>
    <reference name="not.important">
        <block type="core/text_list" name="extra.left.menu" as="extra" />
    </reference>
</awesome_new_container_handle>

And in your other module file add the block like your did.

<default>
    <reference name="extra.left.menu">
        <block type="myextension/some_block" template="some/template.phtml" as="some_name" name="some_name" />
    </reference>
</default>

Related Solutions

Magento – Conditionally add CSS file in layout XML (local.xml)

Bottom line: you need to have a value calculated by PHP, therefore the approach of using a helper is appropriate. I think it makes sense to use the addCss convenience method rather than addItem a it's a little cleaner and should work fine for your needs:

<{handle}>
    <action block="head" method="addCss">
        <stylesheet helper="my_module/my_helper/getFileName" />
    </action>
</{handle}>

Your helper seems to be calculating the path to the CSS files using the design model, but this will be done again by the page/html_head block. Change your helper to simply return the file paths relative to the theme (i.e. not using the design model) and your problem is solved.

Magento – using local.xml to avoid repetition

Yes, you seem to have misunderstood the syntax involved in what you want to do (though it seems you've understood the principles, and that's half the battle!).

Don't use an output block with a typical Magento layout, as the root block is already set as an (the) output block (ref. page.xml):
```
<block type="page/html_head" name="head" output="toHtml"> 
```

You should not be redeclaring the head block; rather, you should reference the one already created (again, ref page.xml):

<!-- <block type="page/html_head" name="head" output="toHtml"> This replaces the original! -->
<reference name="head">
    <action method="addCss"><stylesheet>css/normalize.css</stylesheet></action>
</reference>

Collect would-be-repeated directives in a custom layout update handle and use the <update> directive to include them in other handles:

<UTILITY_HANDLE>
    <reference name="head">
        <action method="addCss"><stylesheet>css/normalize.css</stylesheet></action>
    </reference>
    <reference name="content">
        <block type="core/template" name="prefcentre_regform" template="ps/prefcentre/signup.phtml" />
    </reference>
</UTILITY_HANDLE>
<!-- include the above on catalog product view page -->
<catalog_product_view>
    <update handle="UTILITY_HANDLE" />
</catalog_product_view>

Best Answer

Related Solutions

Magento – Conditionally add CSS file in layout XML (local.xml)

Magento – using local.xml to avoid repetition

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