i have a class: "class ImageBlock extends Block".
this ImageBlock has_one Image.
Image is decorated: Object::add_extension('Image', 'MyImageDecorator');
In MyImageDecorator : function onAfterWrite() { if ( ?????? $this->owner-> ?????? here i need to get 'ImageBlock' }
thanks.timo

You need to create a relation back to the ImageBlock. Something like:

class ImageBlock extends Block {
	private static $db = array(
		'Title' => 'Varchar(128)',
	);
	private static $has_one = array(
		'Image' => 'Image',
	);
}

class ImageExtension extends DataExtension {
	private static $belongs_to = array(
		'ImageBlock' => 'ImageBlock.Image', // reverse $has_one
	);
	public function onAfterWrite() {
		$imgObj = $this->owner; // image object

		echo $imgObj->Title; // image title
		echo $imgObj->ImageBlock()->Title; // imageblock title
	}
}

http://docs.silverstripe.org/en/developer_guides/model/relations/#belongs-to

Though, maybe an Image can appear in multiple ImageBlocks, so it could be better to go with $has_many instead.

class ImageExtension extends DataExtension {
	private static $has_many = array(
		'ImageBlocks' => 'ImageBlock',
	);
	public function onAfterWrite() {
		$imgObj = $this->owner; // image object

		echo $imgObj->Title; // image title
		foreach($imgObj->ImageBlocks() as $block) {
			echo $block->Title; // imageblock title
		}
	}
}