Hi,
after having watched session 230 from this years WWDC (at around 19:00) I wanted to play with the mentioned derived attributes. Sadly I can't find any documentation anywhere, besides the overview from the session in which areas derived attributes may be used:
> The other kind of derivation is a simple transformation of the fields, such as lower casing a tag's name, or canonicalizing some Unicode string. We just saw an example of an aggregate function across a too many relationship in the demo. And lastly, there are global functions such as now that take no parameters at all, which are useful for things like keeping track of when an object was last updated. So now that our controller is wont for nothing, it's time to talk about some more advanced topics and scaling.
Specifically my problem is as follows: I have an item which has many states (over time). The item shall have a property "currentState" which is the latests' state mirrored into the item.
Thanks for your time and support.
