How prevent a model data save using _save_before event

Question

I have create a model which has its own database table. For a customization I need to trigger save_before event of this model.

If one field value is not matched, then the data should not be saved.

My main target is preventing data save using "before save" event

My config.xml code:

<?xml version="1.0" ?>
<config>
    <modules>
        <Amit_Custommodule>
            <version>1.0.0</version>
        </Amit_Custommodule>
    </modules>
    <global>
        <models>
            <custommodule>
                <class>Amit_Custommodule_Model</class>
                <resourceModel>custommodule_resource</resourceModel>
            </custommodule>
            <custommodule_resource>
                <class>Amit_Custommodule_Model_Resource</class>
                <entities>
                    <custommodule>
                        <table>custommodule</table>
                    </custommodule>
                </entities>
            </custommodule_resource>
        </models>
        <resources>
            <custommodule_setup>
                <setup>
                    <module>Amit_Custommodule</module>
                </setup>
                <connection>
                    <use>core_setup</use>
                </connection>
            </custommodule_setup>
            <custommoule_read>
                <connection>
                    <use>core_read</use>
                </connection>
            </custommoule_read>
            <custommodule_write>
                <connection>
                    <use>core_write</use>
                </connection>
            </custommodule_write>
        </resources>
        <events>
            <custommodule_save_before>
                <observers>
                    <custommodule>
                        <type>singleton</type>
                        <class>custommodule/observer</class>
                        <method>customerSaveAfter</method>
                    </custommodule>
                </observers>
            </custommodule_save_before>
    </global>


</config>

Observer.php

<?php
class Amit_Custommodule_Model_Observer
{
public function customerSaveAfter($observer){

if($observer->getEvent()->getMyfield()==MatchWithMyLogic){
}
else
{
/*  i want prevent data base if my business logic is not match here */
}


}
}

Answer 1

If you have a look at the method Mage_Core_Model_Abstract::save, you see this code block:

try {
    $this->_beforeSave();
    if ($this->_dataSaveAllowed) {
        $this->_getResource()->save($this);
        $this->_afterSave();
    }
    $this->_getResource()->addCommitCallback(array($this, 'afterCommitCallback'))
        ->commit();
    $this->_hasDataChanges = false;
    $dataCommited = true;
} catch (Exception $e) {
    $this->_getResource()->rollBack();
    $this->_hasDataChanges = true;
    throw $e;
}

In the _beforeSave() method in the second line, the save_before event is dispatched. Hence, you should be able to just throw an exception in your observer code. This should be catched by the try-catch-block above and should prevent the model to save.

Another possibility is the _dataSaveAllowed field. You can set it to false in your observer code. This will prevent the model to save. And this field is exactly designed for this purpose as the PHP doc reveals:

/**
 * Flag which can stop data saving after before save
 * Can be used for next sequence: we check data in _beforeSave, if data are
 * not valid - we can set this flag to false value and save process will be stopped
 *
 * @var bool
 */
protected $_dataSaveAllowed = true;

Answer 2

In case you need to prevent the save method to execute for a core model (i.e. Catalog/Product), you can use reflection to set "$_dataSaveAllowed" to false:

public function catalogProductSaveBefore($observer)
{
    try {
        $product = $observer->getProduct();

        $reflectionClass = new ReflectionClass('Mage_Catalog_Model_Product');
        $reflectionProperty = $reflectionClass->getProperty('_dataSaveAllowed');
        $reflectionProperty->setAccessible(true);
        $reflectionProperty->setValue($product, false);
    } catch (Exception $e) {
            Mage::log($e->getMessage());
    }

    return $this;
}

Answer 3

You should try @Simon answer first. But if you need to still go for save in both condition, then you can use this cocept

<?php
class Amit_Custommodule_Model_Observer
{
    public function customerSaveAfter($observer)
    {

        if ($observer->getEvent()->getMyfield() == MatchWithMyLogic) {
            //do some other works
            //save data normally
        } else {
            //defines your modules model
            $model = Mage::getModel('model_alias/entity');
            //get entity id that is trying to save if any
            $id = (int)$observer->getEvent()->getEntityId();
            if ($id >= 0 ) {
                //load the correspondign model and retrieve data
                $data = $model->load($id)->getData();

                //set this value to the current object that is trying to save
                $observer->getEvent()->setData($data); 
            } else {
                //set null value for all fields for new entity
                $observer->getEvent()->setData(null);
            }
        }
    }
}

What this method does is, it will first collect data that is correspond to the entity that is going to save and then set current data with that value. This results into save the previous value itself into the database. If there is no entity id present, that means its a new entity. So save null values for that field

EDIT

My friends Simon and AmitBera got confused on this part

else {
        //set null value for all fields for new entity
        $observer->getEvent()->setData(null);
}

So it would be good to explain this part little bit. Suppose the table has two fiels field_one and field_two. In that case, for a new entity (means this has no entry in database), we can set those values like this.

 $observer->getEvent()->setEntityOne('');
  $observer->getEvent()->setEntityTwo('');

This will erase the value that passed and set null value. So during save action, this empty values will be stored in database.

Take idea that I am trying to convey and please don't judge on the basis of demo code that I have provided :)

Answer 4

This may affect more than just the customer object you're trying to prevent from saving, but you can do this in your observer to prevent the save from being applied in the database.

$customer->getResource()->rollBack();
Mage::throwException('Invalid customer account information');

The thrown exception alone won't do it, so you must attempt to rollback the transaction with InnoDB. However, there might be more than just this customer account being modified/created in that transaction, so use this with caution.