Method output arguments return <nil> Value() for ExtensionObject arrays representing custom structure dataTypes #768
Description
When calling a method whose output argument[0] is an array of custom structure dataType values, the corresponding output argument returns a slice of []*ua.ExtensionObject, where the ua.ExtensionObject.Value() == nil for each slice element. The same method called from e.g. UaExpert returns the correct decoded custom structure; that is the method returns the correct []*ua.ExtensionObject. Tested with multiple clients on multiple custom OPC UA servers. As a result, the ExtensionObject value cannot be decoded.
pseudo code:
...
oID := objectNodeId
mID := methodNodeId // method with zero input arguments; one output argument
req := &ua.CallMethodRequest{
ObjectID: oID,
MethodID: mID,
InputArguments: []*ua.Variant{},
}
resp, err := c.Call(ctx, req)
if err != nil {
log.Fatal(err)
}
if got, want := resp.StatusCode, ua.StatusOK; got != want {
log.Fatalf("got status %v want %v", got, want)
}
out := resp.OutputArguments[0].Value()
// first output argument shall be an array of values of a custom structure dataType;
// thus encoded as extensionObjects
extObjects, ok := out.([]*ua.ExtensionObject) // works up to here;
// ...error handling omitted
for _, extObj range extObjects {
value := extObj.Value(). // value is always nil??
}