Recommended way to set prototype of custom JavaScript type?

[EnCey]

I've followed the example outlined in the Wiki about UuidInstance.

It shadows the internal _prototype field:

protected override ObjectInstance GetPrototypeOf() => _prototype;
internal ObjectInstance _prototype;

However, I noticed that ObjectInstance uses the internal _prototype field in other methods as well, like SetPrototypeOf.
Won't I get in hell's kitchen by only partially introducing my own _prototype field?

I'm wondering why not just to call SetPrototypeOf on the UuidInstance in UuidConstructor, i.e. instead of:

jint/Jint.Tests/Runtime/Domain/UuidConstructor.cs

Line 66 in 11b0173

public UuidInstance Construct(JsUuid uuid) => new UuidInstance(Engine) { PrimitiveValue = uuid, _prototype = PrototypeObject };

something like this:

public UuidInstance Construct(JsUuid uuid) {
  var instance = new UuidInstance(Engine) { PrimitiveValue = uuid };
  instance.SetPrototypeOf(PrototypeObject);
  return instance;
}

update: it just occurs to me, if not for the PrimitiveValue property on UuidInstance, do I even need to create a custom implementation of ObjectInstance ? Wouldn't a Prototype and Consturctor suffice?

[lahma]

Here's an alternative approach jos JS UUID kind of integration: #1183 . Options has wrap object handler callback that you could also use to set prototypes.

[EnCey]

Thanks for the tips. I'm trying to create an object with methods that return promises, which internally call async .NET methods: foo.load(...).then(result => ...)
Using TypeDescriptor / TypeReference to build a mapping to async .NET won't work out of the box, I need to inject some custom code that takes care of the Task/Promise handling.

Do you see a problem if I use SetPrototypeOf() on my custom ObjectInstances ?

[EnCey]

I only have a very rudimentary understanding of the API as of yet, but could the ObjectInstance ctor perhaps be extended to allow passing a specific prototype?

        internal ObjectInstance(
            Engine engine,
            ObjectClass objectClass = ObjectClass.Object,
            InternalTypes type = InternalTypes.Object,
+           ObjectInstance? prototype = null)
            : base(type)
        {
            _engine = engine;
            _class = objectClass;
            // if engine is ready, we can take default prototype for object
-           _prototype = engine.Realm.Intrinsics?.Object?.PrototypeObject;
+           _prototype = prototype ?? engine.Realm.Intrinsics?.Object?.PrototypeObject;
            Extensible = true;
        }

[lahma]

SetPrototypeOf is the "standard" way of doing things as it's also exposed on JS side. So I would recommend using it unless there's some blocker I'm not aware of. C# interop can have it rough edges, especially as you are working with the async world here.

[EnCey]

👍 I'll go with SetPrototypeOf then