Working with inheritance

Flextrine supports class table inheritance (CTI) and single table inheritance (STI). You should understand how to map inheritance in Doctrine before reading this chapter.

Using inheritance in Flextrine

Inheritance in Flextrine is implemented using interfaces. For example, if you have a parent entity Page and two child entities WebPage and DesktopPage, then this will generate the following AS3 structure:

public interface Page { }
public class WebPage implements Page { }
public class DesktopPage implements Page { }

This means that you can't treat Page as a real entity from within Flextrine - in effect the parent class is treated as abstract from within Flextrine.

In this situation is would actually be possible to treat Page as a real entity within Doctrine, so its possible that Flextrine will change the handling of inheritance in a later version. However, this inheritance system has been sufficient for the real-world situations I have so far encountered.

Inheritance querying

I have found inheritance to be a powerful tool for allowing different entity classes to be queried in a single collection. For example, we could get all Pages with the following query:

em.select(new Query("SELECT p FROM " + QueryUtil.getDQLClass(Page) + " p")).addResponder(new AsyncResponder(onResult, onFault));

private function onResult(e:ResultEvent, token:Object):void {
	var pages:Array = e.result;

	// pages will contain a selection of WebPages and DesktopPages
}