目录

Wrapping a Native Object in a Sendable ArkTS Object

When to Use

You can call napi_wrap_sendable to bind an ArkTS Sendable object to a native C++ object. Then, call napi_unwrap_sendable to obtain the C++ object bound to the ArkTS object and perform operations on the C++ object.

Example

  1. Declare the APIs, configure compile settings, and register the module.

    Declare the APIs.

    // index.d.ets
@Sendable
export class MyObject {
  constructor(arg: number);
  plusOne(): number;

  public get value(): number;
  public set value(newVal: number);
}

    Configure compile settings.

    # the minimum version of CMake.
cmake_minimum_required(VERSION 3.5.0)
project(napi_wrap_sendable_demo)

set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})

if(DEFINED PACKAGE_FIND_FILE)
    include(${PACKAGE_FIND_FILE})
endif()

include_directories(${NATIVERENDER_ROOT_PATH}
                    ${NATIVERENDER_ROOT_PATH}/include)

add_definitions("-DLOG_DOMAIN=0x0000")
add_definitions("-DLOG_TAG=\"testTag\"")

add_library(entry SHARED napi_init.cpp)
target_link_libraries(entry PUBLIC libace_napi.z.so libhilog_ndk.z.so)

    Register the module.

    // napi_init.cpp
#include "napi/native_api.h"
#include "hilog/log.h"

// A native class. Its instance is wrapped in a Sendable ArkTS object.
class MyObject {
public:
    static napi_value Init(napi_env env, napi_value exports);
    static void Destructor(napi_env env, void *nativeObject, void *finalize_hint);

private:
    explicit MyObject(double value_ = 0);
    ~MyObject();

    static napi_value New(napi_env env, napi_callback_info info);
    static napi_value GetValue(napi_env env, napi_callback_info info);
    static napi_value SetValue(napi_env env, napi_callback_info info);
    static napi_value PlusOne(napi_env env, napi_callback_info info);

    double value_;
    napi_env env_;
};

static thread_local napi_ref g_ref = nullptr;

MyObject::MyObject(double value) : value_(value), env_(nullptr) {}

MyObject::~MyObject() {}

void MyObject::Destructor(napi_env env, void *nativeObject, [[maybe_unused]] void *finalize_hint) {
    OH_LOG_INFO(LOG_APP, "MyObject::Destructor called");
    reinterpret_cast<MyObject *>(nativeObject)->~MyObject();
}

napi_value MyObject::Init(napi_env env, napi_value exports) {
    napi_value num = nullptr;
    napi_status status = napi_create_double(env, 0, &num);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_create_double fail");
        return nullptr;
    }
    napi_property_descriptor properties[] = {
        {"value", nullptr, nullptr, GetValue, SetValue, nullptr, napi_default, nullptr},
        {"plusOne", nullptr, PlusOne, nullptr, nullptr, nullptr, napi_default, nullptr},
    };

    napi_value cons = nullptr;
    // Define a Sendable class MyObject.
    status = napi_define_sendable_class(env, "MyObject", NAPI_AUTO_LENGTH, New, nullptr,
                            sizeof(properties) / sizeof(properties[0]), properties, nullptr, &cons);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_define_sendable_class fail");
        return nullptr;
    }

    status = napi_create_reference(env, cons, 1, &g_ref);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_create_reference fail");
        return nullptr;
    }
    // Mount the MyObject class to the exports object.
    status = napi_set_named_property(env, exports, "MyObject", cons);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_set_named_property fail");
        return nullptr;
    }
    return exports;
}

EXTERN_C_START
// Initialize the module.
static napi_value Init(napi_env env, napi_value exports) {
    MyObject::Init(env, exports);
    return exports;
}
EXTERN_C_END

// Information about the module. Record information such as the Init() function and module name.
static napi_module nativeModule = {
    .nm_version = 1,
    .nm_flags = 0,
    .nm_filename = nullptr,
    .nm_register_func = Init,
    .nm_modname = "entry",
    .nm_priv = nullptr,
    .reserved = {0},
};

// When the .so file is loaded, this function is automatically called to register the nativeModule module with the system.
extern "C" __attribute__((constructor)) void RegisterObjectWrapModule() { napi_module_register(&nativeModule); }

  2. Wrap a C++ object in a Sendable ArkTS object in a constructor.

    napi_value MyObject::New(napi_env env, napi_callback_info info) {
    OH_LOG_INFO(LOG_APP, "MyObject::New called");

    napi_value newTarget = nullptr;
    napi_status status = napi_get_new_target(env, info, &newTarget);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_get_new_target fail");
        return nullptr;
    }
    if (newTarget != nullptr) {
        // Invoked as the constructor `new MyObject(...)`.
        size_t argc = 1;
        napi_value args[1] = { nullptr };
        napi_value jsThis = nullptr;
        status = napi_get_cb_info(env, info, &argc, args, &jsThis, nullptr);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_get_cb_info fail");
            return nullptr;
        }

        double value = 0.0;
        napi_valuetype valuetype = napi_undefined;
        status = napi_typeof(env, args[0], &valuetype);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_typeof fail");
            return nullptr;
        }
        if (valuetype != napi_undefined) {
            status = napi_get_value_double(env, args[0], &value);
            if (status != napi_ok) {
                napi_throw_error(env, nullptr, "Node-API napi_get_value_double fail");
                return nullptr;
            }
        }

        MyObject *obj = new MyObject(value);

        obj->env_ = env;
        // Use napi_wrap_sendable to wrap obj (the C++ object) in jsThis (the Sendable ArkTS object).
        status = napi_wrap_sendable(env, jsThis, reinterpret_cast<void *>(obj), MyObject::Destructor, nullptr);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_wrap_sendable fail");
            delete obj;
            return nullptr;
        }

        return jsThis;
    } else {
        // Invoked as the plain function `MyObject(...)`.
        size_t argc = 1;
        napi_value args[1] = { nullptr };
        status = napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_get_cb_info fail");
            return nullptr;
        }

        napi_value cons = nullptr;
        status = napi_get_reference_value(env, g_ref, &cons);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_get_reference_value fail");
            return nullptr;
        }
        napi_value instance = nullptr;
        status = napi_new_instance(env, cons, argc, args, &instance);
        if (status != napi_ok) {
            napi_throw_error(env, nullptr, "Node-API napi_new_instance fail");
            return nullptr;
        }

        return instance;
    }
}

  3. Retrieve the C++ object from the Sendable ArkTS object and perform subsequent operations on the C++ object.

    napi_value MyObject::GetValue(napi_env env, napi_callback_info info) {
    OH_LOG_INFO(LOG_APP, "MyObject::GetValue called");

    napi_value jsThis = nullptr;
    napi_status status = napi_get_cb_info(env, info, nullptr, nullptr, &jsThis, nullptr);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_get_cb_info fail");
        return nullptr;
    }

    MyObject *obj = nullptr;
    // Use napi_unwrap_sendable to retrieve obj (the C++ object) previously wrapped in jsThis (the Sendable ArkTS object), and perform subsequent operations.
    status = napi_unwrap_sendable(env, jsThis, reinterpret_cast<void **>(&obj));
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_unwrap_sendable fail");
        return nullptr;
    }
    napi_value num = nullptr;
    status = napi_create_double(env, obj->value_, &num);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_create_double fail");
        return nullptr;
    }

    return num;
}

napi_value MyObject::SetValue(napi_env env, napi_callback_info info) {
    OH_LOG_INFO(LOG_APP, "MyObject::SetValue called");

    size_t argc = 1;
    napi_value value = nullptr;
    napi_value jsThis = nullptr;

    napi_status status = napi_get_cb_info(env, info, &argc, &value, &jsThis, nullptr);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_get_cb_info fail");
        return nullptr;
    }

    MyObject *obj = nullptr;
    // Use napi_unwrap_sendable to retrieve obj (the C++ object) previously wrapped in jsThis (the Sendable ArkTS object), and perform subsequent operations.
    status = napi_unwrap_sendable(env, jsThis, reinterpret_cast<void **>(&obj));
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_unwrap_sendable fail");
        return nullptr;
    }
    status = napi_get_value_double(env, value, &obj->value_);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_get_value_double fail");
        return nullptr;
    }

    return nullptr;
}

napi_value MyObject::PlusOne(napi_env env, napi_callback_info info) {
    OH_LOG_INFO(LOG_APP, "MyObject::PlusOne called");

    napi_value jsThis = nullptr;
    napi_status status = napi_get_cb_info(env, info, nullptr, nullptr, &jsThis, nullptr);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_get_cb_info fail");
        return nullptr;
    }

    MyObject *obj = nullptr;
    // Use napi_unwrap_sendable to retrieve obj (the C++ object) previously wrapped in jsThis (the Sendable ArkTS object), and perform subsequent operations.
    status = napi_unwrap_sendable(env, jsThis, reinterpret_cast<void **>(&obj));
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_unwrap_sendable fail");
        return nullptr;
    }
    obj->value_ += 1;
    napi_value num = nullptr;
    status = napi_create_double(env, obj->value_, &num);
    if (status != napi_ok) {
        napi_throw_error(env, nullptr, "Node-API napi_create_double fail");
        return nullptr;
    }

    return num;
}

  4. ArkTS code:

    import { hilog } from '@kit.PerformanceAnalysisKit';
import { MyObject } from 'libentry.so';

try {
    let object : MyObject = new MyObject(0);
    object.value = 1023.1;
    hilog.info(0x0000, 'testTag', 'MyObject value after set: %{public}s', object.value.toString());
    hilog.info(0x0000, 'testTag', 'MyObject plusOne: %{public}s', object.plusOne().toString());
} catch (error) {
    hilog.error(0x0000, 'testTag', 'Test Node-API error: %{public}s', error.message);
}