如何修复ZeroMQ发行者c++中的运行时错误

I was trying to develop a publisher subscriber model in ZeroMQ, using c++, where I am extracting an object value from a JSON-file and sending it to the other side.

我试图在ZeroMQ中开发一个发布者订阅器模型，使用c++，从json文件中提取一个对象值并将其发送到另一端。

My subscriber part is running well with giving any error. But I am facing the below error in the publisher part: ( in the if statement )

我的订户部分运行良好，没有任何错误。但我在发布者部分(在if语句中)面临以下错误

    src/lib_json/json_value.cpp:1136: Json::Value& 
    Json::Value::resolveReference(const char*, bool): Assertion `type_ == 
    nullValue || type_ == objectValue' failed.
    Aborted (core dumped)

This is my code for publisher:

这是我的出版商代码:

    #include "jsoncpp/include/json/value.h"
    #include "jsoncpp/include/json/reader.h"
    #include <fstream>
    #include "cppzmq/zmq.hpp"
    #include <string>
    #include <iostream>
    #include <unistd.h>

    using namespace std;

    int main () {
      zmq::context_t context(1);
      zmq::socket_t publisher (context, ZMQ_PUB);
      int sndhwm = 0;
      publisher.setsockopt (ZMQ_SNDHWM, &sndhwm, sizeof (sndhwm));
      publisher.bind("tcp://*:5561");
      const Json::Value p;
      ifstream pub_file("counter.json");
      Json::Reader reader;
      Json::Value root;

      if(pub_file != NULL && reader.parse(pub_file, root)) {
      const Json::Value p = root ["body"]["device_data"]["device_status"];
       }

      string text = p.asString();
      zmq::message_t message(text.size());
      memcpy(message.data() , text.c_str() , text.size());
      zmq_sleep (1);
      publisher.send(message);
      return 0;
     }

1 个解决方案

#1

const Json::Value p;
...
if(pub_file != NULL && reader.parse(pub_file, root)) {
    const Json::Value p = root ["body"]["device_data"]["device_status"];
}

string text = p.asString();

When you create another p inside the if statement, this newly declared variable is local just to the scope of the conditional {}-code-block. Change this to a clean assignment to an already declared variable p:

当您在if语句中创建另一个p时，这个新声明的变量仅在条件{}-code-block的范围内是局部的。将其更改为已声明变量p的清洁赋值:

p = root ["body"]["device_data"]["device_status"];

This changes the variable in the outer scope, not declaring a new one inside the inner scope. Also, you should mark the variable const Json::Value p as not const, so you can modify it inside the conditional.

这将更改外部范围中的变量，而不是在内部范围内声明一个新的变量。此外，您应该将变量const Json::Value p标记为not const，以便您可以在条件语句中修改它。