我目前正在使用C ++,从使用ostream写入.txt文件的请求中获取HTTP响应。这是异步发生的,我不想改变它。
完成数据写入后,我想从文件中读取
{"data":{"request":[{"type":"City","query":"London, United Kingdom"}],"weather":[{"date":"2013-04-21","astronomy".....
〜不知怎的〜使用像nlohmann / json这样的外部库或其他(?)来预处理字符串然后
a)将其打印到控制台和 b)将其保存在不同的文件中(pretty.json)
我无法理解使用哪种方法: https://github.com/nlohmann/json
任何想法如何解决这个问题?
我正在考虑逐行获取文件,直到我将EOF变成某种“缓冲区”,然后在其上运行_json并保存可以在控制台上显示的解决方案......
到目前为止我的代码
#include <cpprest/http_client.h>
#include <cpprest/filestream.h>
#include <iostream>
#include <sstream>
#include "json.hpp"
using namespace utility; // string conversion
using namespace web; // URI
using namespace web::http; // HTTP commands
using namespace web::http::client; // HTTP Client features
using namespace concurrency::streams; // Asynch streams, like Node
using json = nlohmann::json;
int main()
{
auto fileStream = std::make_shared<ostream>();
// Open stream to output file.
pplx::task<void> requestTask = fstream::open_ostream(U("results.txt"))
.then([=](ostream outFile)
{
*fileStream = outFile;
http_client client //gets the info
return client.request(methods::GET, stringBuilder.to_string());
})
.then([=](http_response response) // set up response handler
{
printf("Received response status code:%u\n", response.status_code());
return response.body().read_to_end(fileStream->streambuf());
})
.then([=](size_t) // close file stream
{
return fileStream->close();
})
.then([=]()
{
nlohmann::json j;
std::ifstream i;
i.open("results.txt"); // ?? <<< === this is where my question is
});
// Wait for all the outstanding I/O to complete, handle exceptions
try
{
requestTask.wait();
}
catch (const std::exception &e)
{
printf("Error exception:%s\n", e.what());
}
return 0;
}
解决方案:
.then([=]()
{
// read a JSON file
std::ifstream readFromFile("results.txt");
if (readFromFile.is_open()) {
nlohmann::json j;
readFromFile >> j;
// write prettified JSON to another file
std::ofstream writeToFile("pretty.json");
writeToFile << std::setw(4) << j << std::endl;
readFromFile.close();
writeToFile.close();
}
else {
std::cout << "unable to open file";
}
});
答案 0 :(得分:3)
你有两种选择用nlohmann来美化。
使用生成字符串的转储
int indent = 4;
nlohmann::json data;
data.dump(indent);
或者使用流输出重载并设置字段宽度
std::ofstream o("pretty.json");
o << std::setw(4) << data << std::endl;