// To minimize the amount of implementation needed, and simplify inversion of control,
// we provide instantiation routines that fit most types of elements in the right order and
// we provide implemented defaults for interfaces that the element could implement.
// Normally, an element shouldn't have to override instantiate or uninstantiate directly.
public virtual void Instantiate(GraphReference instance)
{
// Create the data for this graph, non-recursively, that is
// required for the nest instantiation, so we do it first.
if (this is IGraphElementWithData withData)
{
instance.data.CreateElementData(withData);
}
// Nest instantiation is a recursive operation that will
// call Instantiate on descendant graphs and elements.
// Because event listening will descend graph data recursively,
// we need to create it before.
if (this is IGraphNesterElement nester && nester.nest.graph != null)
{
GraphInstances.Instantiate(instance.ChildReference(nester, true));
}
// StartListening is a recursive operation that will
// descend graphs recursively. It must be called after
// instantiation of all child graphs because it will require
// their data. The drawback with this approach is that it will be
// called at each step bubbling up, whereas it will only
// effectively trigger once we reach the top level.
// Traversal is currently O(n!) where n is the number of descendants,
// ideally it would be O(n) if only triggered from the root.
// => Listening has to be implemented by Bolt classes, because Graphs isn't aware of the event system
}
public virtual void Uninstantiate(GraphReference instance)
{
// See above comments, in reverse order.
if (this is IGraphNesterElement nester && nester.nest.graph != null)
{
GraphInstances.Uninstantiate(instance.ChildReference(nester, true));
}
if (this is IGraphElementWithData withData)
{
instance.data.FreeElementData(withData);
}
}