V8 FunctionTemplate Class Instance

I have the following class:

class PluginManager
{
public:
    Handle<Value> Register(const Arguments& args);
    Handle<ObjectTemplate> GetObjectTemplate();
};

I want the Register method to be accessible from JavaScript. I add it to the global object like this:

PluginManager pluginManagerInstance;

global->Set(String::New("register"), FunctionTemplate::New(pluginManagerInstance.Register));

It throws the following error:

'PluginManager::Register': function call missing argument list; use '&PluginManager::Register' to create a pointer to member

I tried to do that, but it doesn't work either. And it's not correct, because I want it to call the Register method of the pluginManagerInstance.

Except for making the Register method static or global, any ideas?

Thanks.

Solution

You're trying to bind two things at once: the instance and the method to invoke on it, and have it look like a function pointer. That unfortunately doesn't work in C++. You can only bind a pointer to a plain function or a static method. So image you add a static "RegisterCB" method and register it as the callback:

static Handle<Value> RegisterCB(const Arguments& args);
...FunctionTemplate::New(&PluginManager::RegisterCB)...

Now where do you get the pluginManagerInstance from? For this purpose, most callback-registration apis in V8 have an additional "data" parameter that will get passed back to the callback. So does FunctionTemplate::New. So you actually want to bind it like this:

...FunctionTemplate::New(&PluginManager::RegisterCB,
                         External::Wrap(pluginManagerInstance))...

The data is then available through args.Data() and you can delegate to the actual method:

return ((PluginManager*)External::Unwrap(args.Data())->Register(args);

This can surely be made a little easier with some macro.