Creating dependency between admin form fields in magento does not work

Question

This is an admin form in which I have added a custom tab in order add some custom fields to it. The form works fine. but I need to add field dependency for some of my fields.

If the field zipbasedprice_isrange is set to yes, then I need to show other two fields & if it is set to no, then only one field should be shown.

How can I implement this using below form?

Field dependencies should be between zipbasedprice_isrange, zipbasedprice_zip, zipbasedprice_zip_from_zip & zipbasedprice_zip_to_zip.

public function getFormHtml() {
        $form = new Varien_Data_Form(
            array('id' => 'edit_form', 'action' => $this->getData('action'), 'method' => 'post')
        );
    
            $this->getLayout()->createBlock('adminhtml/widget_form_renderer_element').
            $this->getLayout()->createBlock('adminhtml/widget_form_renderer_fieldset').
            $this->getLayout()->createBlock('adminhtml/widget_form_renderer_fieldset_element');


    $fieldset = $form->addFieldset('zipbasedprice_fields', array('legend' => Mage::helper('zipbasedprice')->__('Zip Based Price'))
    );

    $default_country = array('label' => 'IN', 'code' => 'India');
    
    $fieldset->addField('zipbasedprice_country', 'select', array(
                    'name' => 'zipbasedprice_country',
                    'label' => Mage::helper('zipbasedprice')->__('Country'),
                    'values'    => Mage::getModel('adminhtml/system_config_source_country')->toOptionArray(),
                    'required' => true,
                    'style' => 'width:275px',
                    'value' => $default_country,
                    'after_element_html' => '<p class="zipbased_comment" style="margin: 0 150px; padding: 3px;"><img style="margin-right: 4px;" src="http://zonepricing.innoexts.com/skin/adminhtml/default/default/images/note_bg.gif" /><small>select the country to apply price</small></p>',
         ));
    
    $regions = array();
    $regions['*'] = '*';
$regionList = Mage::getModel('directory/region')->getResourceCollection()->addCountryFilter('IN')->load();
foreach($regionList as $region){ $regions[$region['code']] = $region['default_name']; }
    
    $fieldset->addField('zipbasedprice_state', 'select', array(
        'name' => 'zipbasedprice_state',
        'label' => Mage::helper('zipbasedprice')->__('Region/State'),
        'values' => $regions,
        'required' => true,
        'style' => 'width:275px',
      ));
    

   $isRange = $fieldset->addField('zipbasedprice_isrange', 'select', array(
        'name' => 'zipbasedprice_isrange',
        'label' => Mage::helper('zipbasedprice')->__('Is Range?'),
        'values' => array(
            array(
                'value' => false,
                'label' => Mage::helper('zipbasedprice')->__('No'),
            ),
            array(
                'value' => true,
                'label' => Mage::helper('zipbasedprice')->__('Yes'),
            )
        ),
       'value' => false,
       'onchange' => 'onIsZipRangeChange()',
       'required' => false,
   'style' => 'width:275px',
      ));
     

    $fieldset->addField('zipbasedprice_zip', 'text', array(
        'name' => 'zipbasedprice_zip',
        'label' => Mage::helper('zipbasedprice')->__('Zip Code'),
        'class' => 'input',
        'required' => true,
    'style' => 'width:268px',
        'value' => '*',
        'maxlength' => 6,
     ));
        
    
     $fieldset->addField('zipbasedprice_zip_from_zip', 'text', array(
        'name' => 'zipbasedprice_zip_from_zip',
        'label' => Mage::helper('zipbasedprice')->__('Zip Code From'),
        'class' => 'input',
        'required' => true,
    'style' => 'width:268px',
        'value' => '*',
        'maxlength' => 6,
     ));
     
      $fieldset->addField('zipbasedprice_zip_to_zip', 'text', array(
        'name' => 'zipbasedprice_zip_to_zip',
        'label' => Mage::helper('zipbasedprice')->__('Zip Code To'),
        'class' => 'input',
        'required' => true,
    'style' => 'width:268px',
        'value' => '*',
        'maxlength' => 6,
     ));
    
    $fieldset->addField('zipbasedprice_price', 'text', array(
        'name' => 'zipbasedprice_price',
        'label' => Mage::helper('zipbasedprice')->__('Price'),
        'class' => 'input',
        'required' => true,
        'style' => 'width:268px',
        'value' => '0.00',
     ));
    
    $fieldset->addField('zipbasedprice_apply', 'select', array(
        'label' => Mage::helper('zipbasedprice')->__('Apply'),
        'name' => 'zipbasedprice_apply',
        'required' => false,
        'values' => array(
            array(
                'value' => 'fixed',
                'label' => Mage::helper('zipbasedprice')->__('Fixed'),
            ),
            array(
                'value' => 'percentage',
                'label' => Mage::helper('zipbasedprice')->__('Percentage'),
            )
        ),
        'required' => 1,
        'value' => 1,
        'style' => 'width:275px',
    ));
            
    return $form->toHtml();
}

Answer 1

There are different method to do this. Easiest and simplest method would be add an onclick property to the field to which another field depend upon. ie

$fieldset->addField('zipbasedprice_isrange', 'select', array(
    'name' => 'zipbasedprice_isrange',
    'label' => Mage::helper('zipbasedprice')->__('Is Range?'),
    ......
    'onclick' => someFunction();

and then define that someFunction() to achieve what you need.

Another alternative solution is shown in this thread