Layout getBlock is always returning false

Question

I have overridden a core file with my own file. This part is working correctly.

<adminhtml>
    <rewrite>
       <catalog_category_tabs>MyModule_Adminhtml_Block_Tabs</catalog_category_tabs>
    </rewrite>
</adminhtml>

However when trying to add a custom tab with a block for content, I'm running into issues.

class MyModule_Adminhtml_Block_Tabs extends Mage_Adminhtml_Block_Catalog_Category_Tabs
    protected function _prepareLayout()
    {
        // ...
        // dispatch event add custom tabs
         Mage::dispatchEvent('adminhtml_catalog_category_tabs', [
            'tabs' => $this,
        ]);

        // My tab
        $this->addTab('custom', [
            'label'   => Mage::helper('catalog')->__('Custom Tab'),
            'content' => $this->getLayout()->createBlock(
                'adminhtml/tab_custom',
                'category.custom.grid'
            )->toHtml(),
        ]);

        return parent::_prepareLayout();
    }

The createBlock method is returning false.

The referenced file is at MyModule/Adminhtml/Block/Tab/Custom.php. Is there something I'm missing?

Answer 1

In magento, rewrite not means to rewrite all file under in this class.

In there,you have trying to call block class MyModule/Adminhtml/Block/Tab/Custom.php using block type adminhtml/tab_custom.

Using adminhtml/tab_custom block type magento call block class Mage_Adminhtml_Block_Tab_Custom .And that class does not exit at system. that why you did not get false return.

Solution

- Define block type for your module

define the block type of module MyModule_Adminhtml ,so that class this block class by a block type:

<global>
<blocks>
    <mymodule>
    <class>MyModule_Adminhtml_Block</class>
    </mymodule>
    <adminhtml>
        <rewrite>
           <catalog_category_tabs>MyModule_Adminhtml_Block_Tabs</catalog_category_tabs>
        </rewrite>
    </adminhtml>            
</blocks>
</global> 

call that MyModule/Adminhtml/Block/Tab/Custom.php by block type

mymodule/tab_custom.

So change adminhtml/tab_custom to mymodule/tab_custom