harmony 鸿蒙Calling an ArkTS Method with Return Value of a promise Using Node-API

2025-06-12
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Calling an ArkTS Method with Return Value of a promise Using Node-API

When to Use

You can call the ArkTS APIs, which return a promise, in the created ArkTS runtime environment as follows:

Calling an ArkTS Method Asynchronously

Use Node-API to call the ArkTS method that returns a promise in C++. Handle the promise object: Bind the promise object to a C++ callback to process the result returned asynchronously. Convert the data type: In the callback, convert the JavaScript (JS) result to the data that can be used by C++. Conduct thread-safe processing to ensure security of cross-thread operations.

Sample Code

#include "hilog/log.h"
#include "napi/native_api.h"
#include <napi/common.h>
#include <pthread.h>


// Callback for processing a resolved promise.
static napi_value ResolvedCallback(napi_env env, napi_callback_info info)
{
    size_t argc = 1;
    napi_value args[1];
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);


    int result;
    napi_get_value_int32(env, args[0], &result);
    OH_LOG_INFO(LOG_APP, "Promise resolved with result:%{public}d", result);
    return nullptr;
}


// Callback for processing a rejected promise.
static napi_value RejectedCallback(napi_env env, napi_callback_info info)
{
    size_t argc = 1;
    napi_value args[1];
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);


    napi_value error;
    napi_coerce_to_string(env, args[0], &error);
    char errorMsg[1024];
    size_t len;
    napi_get_value_string_utf8(env, error, errorMsg, sizeof(errorMsg), &len);
    OH_LOG_ERROR(LOG_APP, "Promise rejected with error:%{public}s", errorMsg);
    return nullptr;
}


static napi_value CallArkTSAsync(napi_env env, napi_callback_info info)
{
    size_t argc = 1;
    napi_value argv[1] = { nullptr };
    napi_get_cb_info(env, info, &argc, argv, nullptr, nullptr);
    napi_value promise = nullptr;
    napi_call_function(env, nullptr, argv[0], 0, nullptr, &promise);


    napi_value thenFunc = nullptr;
    if (napi_get_named_property(env, promise, "then", &thenFunc) != napi_ok) {
        return nullptr;
    }


    napi_value onResolve = nullptr;
    napi_value onReject = nullptr;
    napi_create_function(env, "onResolve", NAPI_AUTO_LENGTH, ResolvedCallback, nullptr, &onResolve);
    napi_create_function(env, "onReject", NAPI_AUTO_LENGTH, RejectedCallback, nullptr, &onReject);
    napi_value argv1[2] = {onResolve, onReject};
    napi_call_function(env, promise, thenFunc, 2, argv1, nullptr);


    return nullptr;
}


// Register the module.
EXTERN_C_START
static napi_value Init(napi_env env, napi_value exports)
{
    napi_property_descriptor desc[] = {
        {"callArkTSAsync", nullptr, CallArkTSAsync, nullptr, nullptr, nullptr, napi_default, nullptr}
    };
    napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
    return exports;
}
EXTERN_C_END


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 },
};


extern "C" __attribute__((constructor)) void RegisterEntryModule()
{
    napi_module_register(&nativeModule);
}

Declare APIs.

// index.d.ts
export const callArkTSAsync: (func: Function) => object;

Configure compile settings.

Configure the CMakeLists.txt file as follows:

// CMakeLists.txt
# the minimum version of CMake.
cmake_minimum_required(VERSION 3.4.1)
project(myapplication)


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_library(entry SHARED hello.cpp)
target_link_libraries(entry PUBLIC libace_napi.z.so)

Add the following to the build-profile.json5 file of the project.

{
    "buildOption" : {
        "arkOptions" : {
            "runtimeOnly" : {
                "sources": [
                    "./src/main/ets/pages/ObjectUtils.ets"
                ]
            }
        }
    }
}

ArkTS sample code

// index.ets
import testNapi from 'libentry.so'


export function SetTimeout() : Promise<number> {
    return new Promise((resolve) => {
        setTimeout(() => {
            resolve(42);
        }, 1000)
    })
}
testNapi.callArkTSAsync(SetTimeout);