Finalizer only works with mutable structs?

[yuyichao]

@tk3369

I thought all objects have a lifetime – it can be collected by the garbage collector when it’s no longer being referenced. Is that not true?

That’s not true. All ALLOCATIONS have a lifetime. That allocation may or may not have anthing to do with the object. It might not happen at the same time the object is created in the code (it may not even happen) and may or may not end at the same time as the object. This is especially true for immutables and could also be true for mutables.

@leethargo

I want to to use pointer_to_objref with an object (because this is passed through a callback function of a C library).

Pass the object using Any or a correct Ref argument type directly. You almost never want to call pointer_to_objref yourself. (If you are calling it, you are likely doing it wrong for mutable types as well)

@oxinabox

One option is to add a mutable field, e,g a Ref , or a pointer Ptr then attach the finalizer to that.

Depending on what you mean here.

1. Ptr isnt mutable and Ref is an abstract type (neither mutable or immutable).
2. If you mean that adding finalizer to a field of an object for tracking the lifetime of the parent object, then it won’t work. If you make sure that the thing you finalize is limited to that mutable field though it’ll of course work.