I'm climbing the learning curve with embind and having difficulty using
the documentation for Deriving from C++ classes in Javascript
<https://emscripten.org/docs/porting/connecting_cpp_and_javascript/embind.html#deriving-from-c-classes-in-javascript>
to
produce working code. The test embind_test.cpp
<https://github.com/emscripten-core/emscripten/blob/master/tests/embind/embind_test.cpp>
looks like it should be sufficient to fill in the gap in my understanding,
but isn't quite doing it.
My main sticking point right now is that it seems that I am missing some
critical bit of information for how to update Module to include the
prototype for the interface I am trying to extend.
The abstract base class is declared with this:
struct JsPredictInterface
{
explicit JsPredictInterface(const std::string& modelUri);
virtual ~JsPredictInterface();
virtual tz::Tenzor predict(const tz::Tenzor& input) = 0;
std::string mModelUri;
};
(The method predict and in particular its use of tz::Tenzor must still be
implemented, and is shown only to illustrate my intent. I have confirmed
that if I comment out all code related to the predict interface that the
problem below still occurs.)
The bindings for it are declared with this:
struct JsPredictWrapper : public emscripten::wrapper<JsPredictInterface>
{
EMSCRIPTEN_WRAPPER(JsPredictWrapper);
tz::Tenzor predict(const tz::Tenzor& input)
{
return call<tz::Tenzor>("predict", input);
}
};
EMSCRIPTEN_BINDINGS(JsPredictInterface) {
emscripten::class_<JsPredictInterface>("JsPredictInterface")
.function("predict", &JsPredictInterface::predict, emscripten::pure_virtual
())
.allow_subclass<JsPredictWrapper>("JsPredictWrapper", emscripten::
constructor<std::string>())
;
}
I attempt to extend the interface with this code:
EM_JS(void, createImpl, (emscripten::val context, std::string modelPath), {
const assert = require('assert');
assert.ok(Module);
assert.ok(Module.JsPredictInterface);
const PredictorImpl =
Module.JsPredictInterface.extend("JsPredictInterface", {
...
});
const impl = new PredictorImpl(modelPath);
context = {...context, impl};
});
When the function createImpl is called it fails with the assertion
assert.ok(Module.JsPredictInterface).
What am I likely missing to ensure that Module includes the
JsPredictInterface object? Do I have to write the code to update Module? So
far my reading of the documentation has led me to believe that this would
be taking care of by the EMSCRIPTEN_BINDINGS implementation.
Thanks.
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