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external.md

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External (template)

Class Napi::External<T> inherits from class Napi::TypeTaggable.

The Napi::External template class implements the ability to create a Napi::Value object with arbitrary C++ data. It is the user's responsibility to manage the memory for the arbitrary C++ data.

Napi::External objects can be created with an optional Finalizer function and optional Hint value. The Finalizer function, if specified, is called when your Napi::External object is released by Node's garbage collector. It gives your code the opportunity to free any dynamically created data. If you specify a Hint value, it is passed to your Finalizer function. See Finalization for more details.

Note that Napi::Value::IsExternal() will return true for any external value. It does not differentiate between the templated parameter T in Napi::External<T>. It is up to the addon to ensure an Napi::External<T> object holds the correct T when retrieving the data via Napi::External<T>::Data(). One method to ensure an object is of a specific type is through type tags.

Methods

New

template <typename T>
static Napi::External Napi::External::New(napi_env env, T* data);
  • [in] env: The napi_env environment in which to construct the Napi::External object.
  • [in] data: The arbitrary C++ data to be held by the Napi::External object.

Returns the created Napi::External<T> object.

New

template <typename T>
static Napi::External Napi::External::New(napi_env env,
                    T* data,
                    Finalizer finalizeCallback);
  • [in] env: The napi_env environment in which to construct the Napi::External object.
  • [in] data: The arbitrary C++ data to be held by the Napi::External object.
  • [in] finalizeCallback: The function called when the engine destroys the Napi::External object, implementing operator()(Napi::BasicEnv, T*). See Finalization for more details.

Returns the created Napi::External<T> object.

New

template <typename T>
static Napi::External Napi::External::New(napi_env env,
                    T* data,
                    Finalizer finalizeCallback,
                    Hint* finalizeHint);
  • [in] env: The napi_env environment in which to construct the Napi::External object.
  • [in] data: The arbitrary C++ data to be held by the Napi::External object.
  • [in] finalizeCallback: The function called when the engine destroys the Napi::External object, implementing operator()(Napi::BasicEnv, T*, Hint*). See Finalization for more details.
  • [in] finalizeHint: The hint value passed to the finalizeCallback function.

Returns the created Napi::External<T> object.

Data

T* Napi::External::Data() const;

Returns a pointer to the arbitrary C++ data held by the Napi::External object.