liamappelbe
commented
2 years ago You've got some test failures. Take a look at this test to see how to use finalizers. Another example is how we use them in the ObjC bindings:
class _ObjCWrapper implements ffi.Finalizable {
final ffi.Pointer<ObjCObject> _id;
final AVFAudio _lib;
bool _pendingRelease;
_ObjCWrapper._(this._id, this._lib,
{bool retain = false, bool release = false})
: _pendingRelease = release {
if (retain) {
_lib._objc_retain(_id.cast());
}
if (release) {
_lib._objc_releaseFinalizer2.attach(this, _id.cast(), detach: this);
}
}
/// Releases the reference to the underlying ObjC object held by this wrapper.
/// Throws a StateError if this wrapper doesn't currently hold a reference.
void release() {
if (_pendingRelease) {
_pendingRelease = false;
_lib._objc_release(_id.cast());
_lib._objc_releaseFinalizer2.detach(this);
} else {
throw StateError(
'Released an ObjC object that was unowned or already released.');
}
}
}Basically, you need to implement Finalizable in any class that has sole ownership of a native resource. Then in that class's constructor you call finalizer.attach(this, native_pointer, detach: this);, where finalizer is an instance of NativeFinalizer (and is typically a singleton). The native finalizer function you pass to NativeFinalizer must actually be native (ie it can't be implemented in Dart currently), and have this signature void nativeFinalizer(void* native_pointer).
As you can see in the _ObjCWrapper example, it's also standard practice to give users the option of manually releasing the native resource.
modulovalue
Context #95 After this change, the build step for wasmer should reduce to building the wasmer library only. Creating bindings for ios, android and so on should therefore become significantly simpler.
@liamappelbe what do you think? I haven't used this API yet personally, but it seems like it was built for this purpose and is probably a wrapper around the same API that you were using natively.