Working with Primitives Using Node-API

Introduction

Node-API provides APIs for converting data between C/C++ and ArkTS data types and obtaining the ArkTS objects in specified format.

Basic Concepts

Before using Node-API to operate ArkTS objects, you need to understand the following basic concepts:

• Conversion between ArkTS and C/C primitives: You can use Node-API to convert ArkTS values to C/C++ data types, for example, convert an ArkTS value into a C/C++ integer and convert an ArkTS string into a C/C++ string array. You can also convert C/C++ data into an ArkTS value and return the ArkTS value to ArkTS.

Available APIs

The following table lists the APIs for converting data between ArkTS and C/C++ types.

API	Description
napi_coerce_to_bool	Forcibly converts an ArkTS value to an ArkTS Boolean value.
napi_coerce_to_number	Forcibly converts an ArkTS value to an ArkTS number.
napi_coerce_to_object	Forcibly converts an ArkTS value to an ArkTS object.
napi_coerce_to_string	Forcibly converts an ArkTS value to an ArkTS string.
napi_get_boolean	Obtains the ArkTS Boolean value based on the given C Boolean value.
napi_get_value_bool	Obtains the C/C++ equivalent of the given ArkTS Boolean value.
napi_get_global	Obtains an ArkTS global object so that it can be accessed and manipulated in C/C++.
napi_get_null	Obtains the ArkTS null.
napi_get_undefined	Obtains the ArkTS undefined.

Example

If you are just starting out with Node-API, see Node-API Development Process. The following demonstrates only the C++ and ArkTS code involved in related APIs.

napi_coerce_to_bool

Call napi_coerce_to_bool to forcibly convert an ArkTS value to an ArkTS Boolean value.

CPP code:

#include "napi/native_api.h"

static napi_value CoerceToBool(napi_env env, napi_callback_info info)
{
    // Obtain and parse the parameters passed in.
    size_t argc = 1;
    napi_value args[1] = {nullptr};
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
    // Convert the input value to a Boolean value.
    napi_value result = nullptr;
    napi_coerce_to_bool(env, args[0], &result);
    // Return the ArkTS boolean value.
    return result;
}

API declaration:

// index.d.ts
export const coerceToBool: <T>(data: T) => boolean;

ArkTS code:

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

let value = testNapi.coerceToBool<number>(0);
let str = testNapi.coerceToBool<string>('111111111');
let obj = new Object();
let res = testNapi.coerceToBool<Object>(obj);
let result = testNapi.coerceToBool<null>(null);
// false
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_bool:%{public}s', value);
// true
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_bool:%{public}s', str);
// true
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_bool:%{public}s', res);
// false
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_bool:%{public}s', result);

napi_coerce_to_number

Call napi_coerce_to_number to forcibly convert an ArkTS value to an ArkTS number.

CPP code:

#include "napi/native_api.h"

static napi_value CoerceToNumber(napi_env env, napi_callback_info info)
{
    // Obtain and parse the parameters passed in.
    size_t argc = 1;
    napi_value args[1] = {nullptr};
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
    // Convert the input value to a number.
    napi_value result = nullptr;
    napi_coerce_to_number(env, args[0], &result);
    return result;
}

API declaration:

// index.d.ts
export const coerceToNumber: <T>(data: T) => number;

ArkTS code:

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

let value = testNapi.coerceToNumber<string>('2556');
let str = testNapi.coerceToNumber<string>('sssss');
let bool = testNapi.coerceToNumber<boolean>(true);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_number:%{public}d', value);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_number:%{public}d', str);    // NAN is returned.
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_number:%{public}d', bool);   // 1 is returned.

napi_coerce_to_object

Call napi_coerce_to_object to forcibly convert an ArkTS value to an ArkTS object.

CPP code:

#include "napi/native_api.h"

static napi_value CoerceToObject(napi_env env, napi_callback_info info)
{
    // Obtain and parse the parameters passed in.
    size_t argc = 1;
    napi_value args[1] = {nullptr};
    napi_value obj = nullptr;
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
    // Convert the input value to an object.
    napi_coerce_to_object(env, args[0], &obj);
    return obj;
}

API declaration:

// index.d.ts
export const coerceToObject: <T>(data: T) => Object;

ArkTS code:

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

let value = testNapi.coerceToObject<string>('222222');
let result = testNapi.coerceToObject<number>(111);
hilog.info(0x0000, 'testTag', 'Node-API coerceToObject:%{public}s.', typeof result);
if (typeof value === 'object') {
  hilog.info(0x0000, 'testTag', 'Node-API The value is an object.');
} else {
  hilog.info(0x0000, 'testTag', 'Node-API The value is not an object.');
}

napi_coerce_to_string

Call napi_coerce_to_string to forcibly convert an ArkTS value to an ArkTS string.

CPP code:

#include "napi/native_api.h"

static napi_value CoerceToString(napi_env env, napi_callback_info info)
{
    // Obtain and parse the parameters passed in.
    size_t argc = 1;
    napi_value args[1] = {nullptr};
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);
    // Convert the input value to a string.
    napi_value str = nullptr;
    napi_coerce_to_string(env, args[0], &str);
    return str;
}

API declaration:

// index.d.ts
export const coerceToString: <T>(data: T) => string;

ArkTS code:

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

let value = testNapi.coerceToString<number>(212);
let obj = new Object();
let res = testNapi.coerceToString<Object>(obj);
let bool = testNapi.coerceToString<boolean>(false);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_string:%{public}s', value);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_string:%{public}s', typeof res);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_coerce_to_string:%{public}s', bool);

napi_get_boolean

Call napi_get_boolean to obtain the ArkTS Boolean value based on the given C Boolean value.

CPP code:

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

static napi_value GetBoolean(napi_env env, napi_callback_info info)
{
    // Pass in two parameters and parse them.
    size_t argc = 2;
    napi_value argv[2];
    napi_valuetype data, value;
    napi_status status = napi_get_cb_info(env, info, &argc, argv, nullptr, nullptr);
    if (status != napi_ok) {
        OH_LOG_ERROR(LOG_APP, "napi_get_cb_info failed");
        return nullptr;
    }
    // Check the types of the two parameters.
    napi_typeof(env, argv[0], &data);
    napi_typeof(env, argv[1], &value);

    napi_value returnValue = nullptr;
    // Check whether the types of the two parameters are the same and return the result via a Boolean value.
    status = napi_get_boolean(env, data == value, &returnValue);
    if (status != napi_ok) {
        OH_LOG_ERROR(LOG_APP, "napi_get_boolean failed");
        return nullptr;
    }
    // Return the result.
    return returnValue;
}

API declaration:

// index.d.ts
export const getBoolean: <T>(data: T, value: string) => boolean;

ArkTS code:

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

let value = testNapi.getBoolean<number>(1, '1');
let data = testNapi.getBoolean<string>('sss', '1');
hilog.info(0x0000, 'testTag', 'Test Node-API napi_get_boolean:%{public}s', value);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_get_boolean:%{public}s', data);

napi_get_value_bool

Call napi_get_value_bool to obtain the C Boolean equivalent of an ArkTS Boolean value.

CPP code:

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

static napi_value GetValueBool(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);
    bool bool_c = false;
    napi_status status = napi_get_value_bool(env, args[0], &bool_c);
    if (status == napi_boolean_expected) {
        // If napi_get_value_bool is successful, napi_ok is returned. If a non-Boolean value is passed in, napi_boolean_expected is returned.
        return nullptr;
    }
    napi_value boolNapi = nullptr;
    status = napi_get_boolean(env, bool_c, &boolNapi);
    if (status != napi_ok) {
        OH_LOG_ERROR(LOG_APP, "napi_get_boolean failed");
        return nullptr;
    }
    return boolNapi;
}

API declaration:

// index.d.ts
export const getValueBool: (value: boolean | string) => boolean | undefined;

ArkTS code:

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

// Pass in a Boolean value and a non-Boolean value. After the Boolean value is passed in, the Boolean value is returned. After the non-Boolean value is passed in, undefined is returned.
hilog.info(0x0000, 'Node-API', 'get_value_bool_not_bool %{public}s', testNapi.getValueBool('Hello 123'));
hilog.info(0x0000, 'Node-API', 'get_value_bool_true %{public}s', testNapi.getValueBool(true));
hilog.info(0x0000, 'Node-API', 'get_value_bool_false %{public}s', testNapi.getValueBool(false));

napi_get_global

Call napi_get_global to obtain an ArkTS global object. You can use this API to obtain the napi_value that represents an ArkTS global object, so that the global object of the ArkTS runtime can be called by C/C++.

CPP code:

#include "napi/native_api.h"

static napi_value GetGlobal(napi_env env, napi_callback_info info)
{
    napi_value global = nullptr;
    // Obtains a global object.
    napi_get_global(env, &global);
    return global;
}

API declaration:

// index.d.ts
export const getGlobal: () => Object;

ArkTS code:

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

let globalObj = testNapi.getGlobal();
// Check whether the obtained global object has its own properties.
hilog.info(0x0000, 'testTag', 'Test Node-API napi_get_global:%{public}s', globalObj.hasOwnProperty!("undefined"));

napi_get_null

Call napi_get_null to obtain null in ArkTS.

CPP code:

#include "napi/native_api.h"

static napi_value GetNull(napi_env env, napi_callback_info info)
{
    napi_value nullValue = nullptr;
    napi_get_null(env, &nullValue);
    return nullValue;
}

API declaration:

// index.d.ts
export const getNull: () => null;

ArkTS code:

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

let value = testNapi.getNull();
hilog.info(0x0000, 'testTag', 'Test Node-API napi_get_null:%{public}s', value);

napi_get_undefined

Call napi_get_undefined to obtain undefined in ArkTS.

CPP code:

#include "napi/native_api.h"

static napi_value GetUndefined(napi_env env, napi_callback_info info)
{
    // Obtain and parse the parameters passed in.
    size_t argc = 1;
    napi_value args[1] = {nullptr};
    napi_get_cb_info(env, info, &argc, args, nullptr, nullptr);

    napi_value value = nullptr;
    napi_get_undefined(env, &value);
    // Check whether the input parameter is equal to the ArkTS 'undefined' in both the type and value.
    bool isEqual = false;
    napi_strict_equals(env, args[0], value, &isEqual);
    // Return a value based on the strict equality check.
    napi_value result = nullptr;
    // Return true if the two parameters are equal, return false otherwise.
    napi_get_boolean(env, isEqual, &result);
    return result;
}

API declaration:

// index.d.ts
export const getUndefined: (value: undefined) => boolean;

ArkTS code:

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

let data: undefined = undefined;
let value = testNapi.getUndefined(data);
hilog.info(0x0000, 'testTag', 'Test Node-API napi_get_undefined:%{public}s', value);

To print logs in the native CPP, add the following information to the CMakeLists.txt file and add the header file by using #include "hilog/log.h".

// CMakeLists.txt
add_definitions( "-DLOG_DOMAIN=0xd0d0" )
add_definitions( "-DLOG_TAG=\"testTag\"" )
target_link_libraries(entry PUBLIC libace_napi.z.so libhilog_ndk.z.so)