> For the complete documentation index, see [llms.txt](https://xoops.gitbook.io/xoops-modules-cookbook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://xoops.gitbook.io/xoops-modules-cookbook/core-classes/core/key-classes.md).

# Key Classes

## Key Classes/Objects API

**Using Xoops API**

In addition to the Xoops API documentation <http://api.xoops.org/> here we also need guidelines for module writers as to what classes to use when, why, and how, etc. For example:

* XoopsObject Data Access classes

If you create a module class (in the class folder of your module) called `Myclass` that extends `XoopsObject`:

```php
<?php

namespace XoopsModules\Mymodule;

class Myclass extends \XoopsObject
{
    /**
    * Constructor
    **/
    public function __construct() // Constructor
    {
    $this->initVar('my_variable', XOBJ_DTYPE_INT, NULL);
    }
}
```

In a separate file we create a handler called `MyclassHandler` that extends XoopsPersistableObjectHandler:

```php
<?php

namespace XoopsModules\Mymodule;

class MyclassHandler extends \XoopsPersistableObjectHandler
   {
   }
```

you can then obtain a reference to an instance of the handler class like this: In /modules/module/index.php:

```php
<?php

namespace XoopsModules\Mymodule;

$myclassHandler = new Mymodule\MyclassHandler();
```

Built in data object handlers can be obtained via xoops\_gethandler(''). Search for the use of this idiom in other modules for an idea of how these classes let you build data access objects to interface with corresponding database tables.

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![](/files/-M5aqYwM4_aRUSVinGVN)