Class 'Mage_Affiliate_Helper_Data' not found

Question

I am trying to make a module with some settings I can change via system configuration

they explained me here: How to make some parameters editable via admin

However I am having the following problem

Fatal error: Class 'Mage_Affiliate_Helper_Data' not found in /home/theprint/public_html/preprod/app/Mage.php on line 547

The structure is as follows:

Should I create a data.php empty?

http://screencast.com/t/mOnMlNKun

Update 1:

this is my config.xml

  <?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Luisvalencia_Affiliate>
            <version>0.0.1</version>
        </Luisvalencia_Affiliate>
    </modules>
    <global>
        <models>
            <luisvalencia_affiliate>
                <class>Luisvalencia_Affiliate_Model</class>
            </luisvalencia_affiliate>
        </models>
        <helpers>
            <luisvalencia_affiliate>
                <class>Luisvalencia_Affiliate_Helper</class>
            </luisvalencia_affiliate>
        </helpers>
    </global>
    <frontend>
        <events>
            <controller_action_predispatch>
                <observers>
                    <luisvalencia_affiliate>
                        <class>luisvalencia_affiliate/observer</class>
                        <method>captureReferral</method>
                        <type>singleton</type>
                    </luisvalencia_affiliate>
                </observers>
            </controller_action_predispatch>
        </events>
    </frontend>
</config>

Answer 1

As I see that your error is Class 'Mage_Affiliate_Helper_Data' not found that means helper name should be affiliate that means Mage::helper('affiliate'); and need to add this code in config.xml file

    ....
        <global>
....
<!-- add this code in global tag in  global -->
            <helpers>
                 <affiliate>
                       <class>Luisvalencia_Affiliate_Helper</class>
                 </affiliate>
            </helpers>
.....
        </global>

And Need to define helper class and helper file is Data.php(Luisvalencia/Affiliate/Helper/Data.php)

<?php 
class Luisvalencia_Affiliate_Helper_Data extends Mage_Core_Helper_Abstract {
}

Edit:According to your code

<helpers>
            <luisvalencia_affiliate>
                <class>Luisvalencia_Affiliate_Helper</class>
            </luisvalencia_affiliate>
        </helpers>

should be

 <helpers>
                 <affiliate>
                       <class>Luisvalencia_Affiliate_Helper</class>
                 </affiliate>
            </helpers>

Answer 2

Yes you need to define your helper class. This includes two steps

Define helper class inside config.xml

<config>
    <global>
        <helpers>
             <luisvalencia_affiliate>
                   <class>Luisvalencia_Affiliate_Helper</class>
             </luisvalencia_affiliate>
        </helpers>
    </global>
</config>

Declare your Helper Class

location: app/code/community/Luisvalencia/Affiliate/Helper/Data.php

<?php 
class Luisvalencia_Affiliate_Helper_Data extends Mage_Core_Helper_Abstract {
}

Now you can refer you helper like this.

 Mage::helper('luisvalencia_affiliate');

Hope that helps

Answer 3

Yes. Create a Data.php file like

<?php class Luisvalencia_Affiliate_Helper_Data extends Mage_Core_Helper_Abstract {
}

and declare it in your module config too. This normally happens when you try to call __() to translate something.