Pass Entities to a C-extension

[DanRathbun]

@TommyL

I can get a pointer with the above method, but if I cross-check it with the parent of the deleted entity, it points to something else. So I suspect I have a pointer to an opaque internal data structure which is of no use to me.

By the time most deleted/removed observer callbacks fire, the entity/object has already been deleted. So it, and likely it’s parent are pointing to dummy class objects on the Ruby side and perhaps some dummy struct on the C side.

This is the reason why only the ID is passed. It is expected that extensions will be keeping some collection of their own probably keyed by the integer ID, so this will allow a lookup and allow the extension to deal with the removal.

It is not ideal and so requests have been opened in the API tracker. See what I said yesterday in this post …

MaterialsObserver and Undo

There are open issues in the API tracker: Observers for Removed events - Should fire before removal · Issue #402 · SketchUp/api-issue-tracker (github.com) Tracking major events in the lifetime of a Sketchup session · Issue #682 · SketchUp/api-issue-tracker (github.com) Improve documentation for undo handling · Issue #627 · SketchUp/api-issue-tracker (github.com) Basically, the only workaround is for your extension to cache data and state at a higher level. Then in the observer callb…

@TommyL

However, Entities are not inheriting from Entity, so this fails with error code SU_ERROR_INVALID_ARGUMENT.

FYI: The entities objects in Ruby are so called “thinly wrapped” C++ collections.

@TommyL

Is there a complementary API function to SUEntityFromRuby to handle this case?

No. But I think you may be able to work around it. If you keep a hash of objects and their parents keyed by ID. Then pass the parent entity (model or component definition for groups and instances) and on the C-side get the entities collection via the normal C API functions:

• SUModelGetEntities()

• SUComponentInstanceGetDefinition()

  • SUComponentDefinitionGetEntities()

• SUGroupGetEntities() - convenience function to get it’s definition’s entities

It can be more observer code keeping track of everything.