Polymorphism support

[leth]

I am working on it!

I've got rudimentary field inheritance working, but I haven't attempted anything which touches the database yet :P I'll post a link to the branch once I've got something worth sharing.

As always, comments suggestions and feature requests are welcome :)

[creatoro]

Cool :)

[leth]

I've published my branch. I've only gone far enough to support loading models directly, nothing complex yet.

It's a long way off being finished though, and I have the suspicion that there remain better ways of doing things.

There are 3 unit tests on polymorphic modes, currently, the third tests for behaviour I've not implemented yet so only passes for the simplest dataset item.

[leth]

I've made some design decisions which feel kind of major, I'd appreciate some comments on my ideas:

Field inheritance

• Subclasses inherit all fields from the parent class.
• Calling parent::initialize($meta) is optional.
• Classes can re-declare fields declared by parent classes, with some restrictions (fields must be subclass of original types, some options cannot be changed) (these aren't implemented yet)

Subclass discovery

In order for a single db query to return instances of a class and its subclasses we'll need to explicitly join their tables. Therefore we need to know in advance which tables to join.

Since we can't find a list of all subclasses (because they may have not yet been autoloaded) I've decided that subclasses must be explicitly registered in the initialize(...) method.

[leth]

I've pushed subclass detection in query results. It's a bit hacky, but the tests pass now :)

As always, comments welcome!

[creatoro]

Nice work, keep going. I'll go through it when we're ready with the 3.2 branch,