Working with Proxy Using JSVM-API

Introduction

This topic walks you through on how to use JSVM-API to create a proxy instance, check whether the given JSVM_Value is of the proxy type, and obtain the target object from the given proxy.

Available APIs

Example

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

CPP code:

// Define OH_JSVM_CreateProxy.
static JSVM_Value CreateProxy(JSVM_Env env, JSVM_CallbackInfo info) {
    // Pass in two parameters: target and handler.
    size_t argc = 2;
    JSVM_Value args[2] = {nullptr};
    JSVM_CALL(OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr));
    // Call OH_JSVM_CreateProxy to create a proxy for the target object.
    JSVM_Value result = nullptr;
    JSVM_Status status = OH_JSVM_CreateProxy(env, args[0], args[1], &result);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_CreateProxy: failed: %{public}d", status);
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_CreateProxy: success");
    }

    return result;
}

// Define OH_JSVM_IsProxy.
static JSVM_Value IsProxy(JSVM_Env env, JSVM_CallbackInfo info) {
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    JSVM_CALL(OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr));
    // Call OH_JSVM_IsProxy to check whether JSVM_Value is a proxy.
    bool result = false;
    JSVM_Status status = OH_JSVM_IsProxy(env, args[0], &result);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_IsProxy: failed");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_IsProxy: success: %{public}s", result ? "is a proxy" : "is not a proxy");
    }
    JSVM_Value isProxy;
    JSVM_CALL(OH_JSVM_GetBoolean(env, result, &isProxy));
    return isProxy;
}

// Define OH_JSVM_ProxyGetTarget.
static JSVM_Value GetProxyTarget(JSVM_Env env, JSVM_CallbackInfo info) {
    size_t argc = 1;
    JSVM_Value args[1] = {nullptr};
    JSVM_CALL(OH_JSVM_GetCbInfo(env, info, &argc, args, nullptr, nullptr));
    // Call OH_JSVM_ProxyGetTarget to obtain the target object in the proxy.
    JSVM_Value result = nullptr;
    JSVM_Status status = OH_JSVM_ProxyGetTarget(env, args[0], &result);
    if (status != JSVM_OK) {
        OH_LOG_ERROR(LOG_APP, "JSVM OH_JSVM_ProxyGetTarget: failed");
    } else {
        OH_LOG_INFO(LOG_APP, "JSVM OH_JSVM_ProxyGetTarget: success");
    }

    return result;
}

// Register the proxy-related callbacks.
static JSVM_CallbackStruct param[] = {{.data = nullptr, .callback = CreateProxy},
                                      {.data = nullptr, .callback = IsProxy},
                                      {.data = nullptr, .callback = GetProxyTarget}};
static JSVM_CallbackStruct *method = param;
// Aliases for the proxy-related callbacks to be called from JS.
static JSVM_PropertyDescriptor descriptor[] = {
    {"CreateProxy", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
    {"IsProxy", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT},
    {"GetProxyTarget", nullptr, method++, nullptr, nullptr, nullptr, JSVM_DEFAULT}};

const char *srcCallNative = R"JS(
       target = {
         message1: "hello",
         message2: "everyone",
       };

       handler = {
         get(target, prop, receiver) {
           return "world";
         },
       };

       proxy = CreateProxy(target, handler)
       isProxy = IsProxy(proxy)
       target1 = GetProxyTarget(proxy)
)JS";

Expected result:

JSVM OH_JSVM_CreateProxy: success
JSVM OH_JSVM_IsProxy: success: is a proxy
JSVM OH_JSVM_ProxyGetTarget: success

你可能感兴趣的鸿蒙文章

harmony 鸿蒙Node-API

harmony 鸿蒙Building an NDK Project with CMake

harmony 鸿蒙Building an NDK Project with the DevEco Studio Template

harmony 鸿蒙NDK Project Building Overview

harmony 鸿蒙Building an NDK Project with Prebuilt Libraries

harmony 鸿蒙C/C++ Library Mechanisms

harmony 鸿蒙CPU Features

harmony 鸿蒙Creating an NDK Project

harmony 鸿蒙C/C++ Memory Error Detection

harmony 鸿蒙Debugging in DevEco Studio