Proposal: GenericDataObject

Author

David Heath

Date

23 Jul 03

Status

Download a demo here.

Summary

Motivation

An unneccessary amount of effort is involved in coding basic data storage and retrieval for new data object classes.

Opportunity

Much of this code is quite similar, so we could abstract and build at a higher level

Proposal

add a GenericDataObject class which would handle object storage/retrieval.

Details

This proposal is to add a class called GenericDataObject in /classes/genericdataobject.php. I implemented an experimental version in the worldpay transaction class for the online donations module. This key data structure in this class is $parameterMetadata, which looks like this:

class eZWorldPayTransaction {

    var $primaryKey = 'cartId';

    var $parameterMetadata = array(
        'cartId' => DBSTORAGE_INT4,
        'instId' => DBSTORAGE_INT4,
        'description' => DBSTORAGE_STRING,
        'amount' => DBSTORAGE_DECIMAL,
        'currency' => DBSTORAGE_STRING,
        'accId' => DBSTORAGE_INT4,
        'authMode' => DBSTORAGE_INT4,
        ...
        );

    function setAttribute($name, $value) {
        if (array_key_exists($name, $this->parameterMetadata)) {
            $this->$name = $value;
        }
    }

    function getAttribute($name) {
        if (array_key_exists($name, $this->parameterMetadata)) {
            return $this->$name;
        }
        else {
            return false;
        }
    }
}

This data structure is used to automate the insert/delete/update operations.

What does this achieve:

• only have to change this data structure to add another attribute (don't have to modify insert+update sql)
• allows data validation of parameters based on the metadata, which is not always done by the programmer

For the GenericDataObject, the derived class would provide $parmeterMetadata (either set it in the constructor, or have it taken from an overridden method). The derived class would not need to implement fill/get/store/delete. The derived class could override setAttribute/getAttribute if special behaviour was needed for particular attributes.