# XoopsObject & XoopsObjectHandler

XOOPS' early data persistence architecture was based on the [Data Mapper pattern](http://martinfowler.com/eaaCatalog/dataMapper.html), with two abstract classes to aid in the class development **XoopsObject** and **XoopsObjectHandler**

* XoopsObject: abstract class of Data Object
* XoopsObjectHandler: Mapper. An abstract class that saves XoopsObject in DB or rebuilds XoopsObject from DB 

![](https://879096944-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M5_mFcvcxsA3M1QhbWd%2F-M5b2crDSTdxTdAndKG-%2F-M5b2fILg_qP-PDV4l-9%2FXoopsDataMapperArchitecture.png?generation=1587645695065309\&alt=media)

The idea behind them is that a class can extend **XoopsObject** to describe an object, whereas extending **XoopsObjectHandler** will give more like an interface for handling the objects, i.e. get, insert, delete and create objects.

E.g. for a `ThisObject` class, you can make a `ThisObjectHandler` to get, insert, delete and create `ThisObject` objects.

The advantages of extending these two classes are for **XoopsObject**:

* Automatic access (inheritance) to methods, easing the assignment/retrieval of variables
* Automatic access to methods for cleaning/sanitizing variables

and for **XoopsObjectHandler**:

* A place to put all those functions working with more than one object i.e. (e.g. a "getAllObjects()" function).

These functions will become easier to track down in the file system (since they are connected to a class, it is just a matter of finding the class and not going through the function files in the module/core/PHP native in search for it.

An additional idea is that the **XoopsObjectHandler**-extending class should be a **Data Access Object**, i.e. the class, which handles database calls - and leaving the **XoopsObject**-extending class to have object-describing methods, such as methods which handle and manipulate variables, calling methods on the handler for retrieving, updating and inserting data in the database.

In XOOPS 2.3 we've added a new enhanced version of the **XoopsObjectHandler**, the **XoopsPersistableObjectHandler**, that incorporated features/characteristics from the [**Repository Pattern**](https://martinfowler.com/eaaCatalog/repository.html)