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 C++ to call the ArkTS method that returns a promise through the Node-API.

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++.

Sample Code

• Module registration

  #include "hilog/log.h"
  #include "napi/native_api.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] = { nullptr };
      napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
  
      int result = 0;
      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] = { nullptr };
      napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
  
      napi_value error = nullptr;
      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);
      // Initialize the promise object.
      napi_value promise = nullptr;
      napi_call_function(env, nullptr, argv[0], 0, nullptr, &promise);
  
      // Initialize the thenFunc object.
      napi_value thenFunc = nullptr;
      if (napi_get_named_property(env, promise, "then", &thenFunc) != napi_ok) {
          return nullptr;
      }
      // Initialize the onResolve object.
      napi_value onResolve = nullptr;
      // Initialize the onReject object.
      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);
      // Create a parameter array.
      napi_value thenArgv[2] = {onResolve, onReject};
      napi_call_function(env, promise, thenFunc, 2, thenArgv, nullptr);
  
      return nullptr;
  }
  
  // Register the module.
  EXTERN_C_START
  static napi_value Init(napi_env env, napi_value exports)
  {
      // Initialize the attribute description array.
      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
  
  // Initialize the module.
  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);
  }
  

• API declaration

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

• 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_definitions( "-DLOG_DOMAIN=0xd0d0" )
  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)
  

• 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);