How to set extension enable and disable

Question

Have an extension and want to enable it if $field1 == $field2 and if not extension be disable.

can enable it with line below but can not disable it when if is not true!

protected function _beforeSave()
{
    $value = $this->getValue();
    $fieldConf = $this->getFieldConfig();

    if ($value) {
        try {

            $fields2 = Mage::getStoreConfig('carriers/module/fields2');
            $fields1 = Mage::getStoreConfig('carriers/module/fields1');

            $condition = empty($fields2) || !$fields2 || empty($fields1) || !$fields1;

            if ($condition) {
                $err = Mage::helper('module')->__('extension not registered.');
                Mage::throwException($err);
            }

            if($field1 == $field2) {
                Mage::getConfig()->saveConfig('carriers/module/active', 1)->reinit();
                Mage::app()->getConfig()->reinit();
            } else {
                Mage::getConfig()->saveConfig('carriers/module/active', 0)->reinit();
                Mage::app()->getConfig()->reinit();
                $err = Mage::helper('module')->__('Is not valid and Disabled.');
                Mage::throwException($err);
            }
        }
        catch (Exception $e) {
            Mage::throwException($e->getMessage());
            return $this;
        }
    }

    return $this;
}

Answer 1

I don't believe that determining whether to enable or disable an extension in the method logic is a good approach.

The extension you want to enable or disable should have an entry point, at which it checks for your $field1 == $field2 condition. If it it holds true, it should go on with its processes; otherwise, it should just return.

If you really need to do this "on the fly," I suggest checking $field1 == $field2 right after Magento either loads the cached configurations or loads them all at once with something like..

Mage::getConfig()->setNode($nodePathToYourExtension, 'false', true)

Offhand, it should be somewhere in Mage_Core_App::run().