I have not found a way to create a destroy hook for objects that inherit from RootObj (or even futher down an inheritance hierarchy):
type Foo = ref object of RootObj
proc `=destroy`(foo: Foo) =
discard
Is there a way to accomplish this?
For more context, I have an object which holds a data structure from SDL that must be freed. When my object is destroyed, I need to call freeFoo on the object.
I do not know if this is the proper way of doing it but the following does work.
type
FooObj = object of RootObj
Foo = ref FooObj
proc `=destroy`(foo: var FooObj) =
echo "Destroy"
var foo = Foo()
That does appear to work, but I'm running into an issue trying it for my particular use case:
Why would there be an implicit construction of the =destroy hook, perhaps because Image is a ptr object or Font is a pointer?
Even if that's the case, how would I gain control of the deconstruction so I can perform my own or additional operations?
I don't think the GC has anything to do with ptr or pointer. They're simply untraced. The error message says =destroy is constructed at line 14, where TextBox is. Maybe =destroy should be defined before TextBox?
I think it would be enough to place the destroy hook before the first usage of the TextBox type. Essentially as Nim reads through this it sees that it needs a destructor for that type, sees that it doesn't have one, and creates one implicitly. Then it encounters yours and fails because it already has the one it created. These =destroy hooks should be created as early as possible in your code, I remember reading this in some of the documentation, but not entirely sure where.
Thanks, that worked. I did not expect that behavior