Do we need `wrapper_`?

[Gabriel Schulhof]

In our ObjectWrap N-API examples we store the napi_ref returned from napi_wrap() in the native object instance although we never use it. To napi_delete_reference() in the destructor we need to also store the napi_env on the native instance – a practice we discourage.

Do we do this for illustration purposes? Can we remove this, since wrapper_ is not being used anywhere?

[Gabriel Schulhof]

This is the extent to which we use wrapper_ and env_:

node-addon-examples/6_object_wrap/napi/myobject.cc

Lines 6 to 11 in dc86a66

 MyObject::MyObject(double value) 
     : value_(value), env_(nullptr), wrapper_(nullptr) {} 
  
 MyObject::~MyObject() { 
   napi_delete_reference(env_, wrapper_); 
 } 

and

node-addon-examples/6_object_wrap/napi/myobject.cc

Lines 72 to 78 in dc86a66

 obj->env_ = env; 
 status = napi_wrap(env, 
                    jsthis, 
                    reinterpret_cast<void*>(obj), 
                    MyObject::Destructor, 
                    nullptr,  // finalize_hint 
                    &obj->wrapper_); 

[Gabriel Schulhof]

Compare with the Nan implementation. The use of the persistent reference may stem from there. If so, it may be a good time to diverge, especially since we document that we discourage storing the napi_env.

[Gabriel Schulhof]

In fact, none of the Nan examples store a persistent reference to the JS instance. We should remove it.