<?php
class SiteConfigOverride extends DataObjectDecorator{
	function extraStatics() {
		return array(
				 'db' => array(
					"Description" 						=> "Varchar(255)",
					"ContactNumber" 					=> "Varchar(255)",
					'WebsiteFooter'						=> 'HTMLText',
			),
			 'has_many' => array(
							"TestObject" 				=> "TestObject",
			),
		);
	}

	public function updateCMSFields(FieldSet &$fields) {
		$fields->addFieldToTab("Root.Main", new TextField("Description"));
		$fields->addFieldToTab("Root.Main", new TextField("ContactNumber"));
		$fields->addFieldToTab("Root.Main", new HtmlEditorField("WebsiteFooter"));

		$tablefield = new HasManyComplexTableField(
			$this,
			'TestObject',
			'TestObject'
		);

        $fields->addFieldToTab( 'Root.TestObject', $tablefield );
	}
}




<?php

class TestObject extends DataObject {
	static $db = array(
		'Name' => 'Text',
		'Description' => 'Text',
	);

	static $has_one = array(
		'SiteConfig' => 'SiteConfig',
	);

}