Question

How can I call helper of another module in my module?

When I try

Mage::helper(‘helperclass’)->getValueClass(”,$id)

It gives me error:

Fatal error: Class ‘Mage_Helperclass_Helper_Data’ not found in C:\wamp\www\example\app\Mage.php on line 516

The helper class name is Test_Helperclass_Helper_Data.

Answer 1

This is the correct way to call a helper, but your error suggests that you’ve not set up your module properly. I presume your module exists in app/code/local/Test/Helperclass, and that you have enabled your module with a app/etc/modules/Test_Helperclass.xml file.

When you call Magento’s factories, such as Mage::getModel(), Mage::getSingleton(), or Mage::helper(), you don’t provide the full class name, but a reference to the class you’d like to instantiate.

This has the format modulename/classname.

In our case, the module name is helperclass (doesn’t have to bare any relationship to the actual name of the module, it could just as well be foobar), and our class name is data. So we’re essentially calling Mage::helper('helperclass/data'), but Magento lets us shorten that down to Mage::helper('helperclass').

We need to tell Magento the rule behind expanding helperclass/data -> Test_Helperclass_Helper_Data. We do this in the module configuration file at app/code/local/Test/Helperclass/etc/config.xml:

<?xml version="1.0"?>
<config>
    ...
        <global>
            <helpers>
                <!-- Here is where we define the mapping rule -->
                <helperclass>
                    <class>Test_Helperclass_Helper</class>
                </helperclass>
            </helpers>
        </global>
    ...
</config>