Finding instances

Selecting instances

To update or read data in the class model, it is first necessary to find the relevant instances. In fact, figuring out how to specify exactly the instances you want (or don’t want) is the most challenging aspect of writing an activity.

Where to start?

The approach you take depends on where your search starts. There are a handful of potential starting points. For example, you might want to select a subset of instances within a known class. Or you might have a set of instances of some class already and want to traverse from those across one or more relationships to find related instances in the same or some other class. Finally, you might start from an assigner state machine and want to select one or more instances that it manages.

Let’s explore how to proceed from each possible origin.

Starting from a class

Starting from an instance set

Starting from an assigner