How to solve Uncaught error

Question

How to solve below error

Fatal error: Uncaught Error: Class 'Mage_Companyname_Deliverydate_Block_Adminhtml_Mappingdate' not found in \app\code\core\Mage\Core\Model\Layout.php on line 590

below is my files

app/code/local/Companyname/Deliverydate/Block/Adminhtml

<?php

class Companyname_Deliverydate_Block_Adminhtml_Mappingdate  
    extends Mage_Adminhtml_Block_System_Config_Form_Field_Array_Abstract
{

    public function __construct()
    {
        $helper = Mage::helper('deliverydate');

        $this->addColumn('column_one', array(
            'style' => 'width:200px',
            'label' => $helper->__('Column One'),
        ));

        $this->addColumn('column_two', array(
            'style' => 'width:200px',
            'label' => $helper->__('Column Two'),
        ));

        $this->addColumn('column_three', array(
            'style' => 'width:80px',
            'label' => $helper->__('Column Three'),
        ));

        parent::__construct();
    }
}

Config.xml

<global>
 <blocks>
  <deliverydate>
     <class>Companyname_Deliverydate_Block</class>
  </deliverydate>
 </blocks>
  <helpers>
      <deliverydate>
            <class>Companyname_Deliverydate_Helper</class>
      </deliverydate>
   </helpers>
<default>
            <deliverydate>
                <deliverydate_general>
                    <enabled>0</enabled> 
                    <on_which_page>1</on_which_page>   
                    <deliverydate_format>d/M/Y</deliverydate_format>
                    <deliverytime_format>g:i a</deliverytime_format>
                    <deliverydate_dayoff></deliverydate_dayoff>
                    <mapping_date></mapping_date>
                </deliverydate_general>
            </deliverydate>
        </default>
</global>

system.xml

<config>
    <sections>
        <deliverydate translate="label" module="deliverydate">
            <class>separator-top</class>
            <label>Delivery Date</label>
            <tab>Companyname</tab>
            <sort_order>130</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>
                <deliverydate_general translate="label">
                    <label>General</label>
                    <frontend_type>text</frontend_type>
                    <sort_order>10</sort_order>
                    <show_in_default>1</show_in_default>
                    <show_in_website>1</show_in_website>
                    <show_in_store>1</show_in_store>
                    <fields>
      <mapping_date>
       <label>Date Off</label>                  <frontend_model>companyname_deliverydate/adminhtml_mappingdate</frontend_model>                          <backend_model>adminhtml/system_config_backend_serialized_array</backend_model>
                            <sort_order>10</sort_order>
                            <show_in_default>1</show_in_default>   <show_in_website>1</show_in_website>
                            <show_in_store>0</show_in_store>
                        </mapping_date>
                    </fields>
                </deliverydate_general>
            </groups>
        </deliverydate>
    </sections>
</config>

Answer 1

you can replace below line

<frontend_model>companyname_deliverydate/adminhtml_mappingdate</frontend_model>

to

<frontend_model>deliverydate/adminhtml_mappingdate</frontend_model>