I'm new to c++ and trying to use nlohmann library and I'm quite stuck. I want to modify array of objects from json.
json =
{
"a": "xxxx",
"b": [{
"c": "aaa",
"d": [{
"e": "yyy"
},
{
"e": "sss",
"f": "fff"
}
]
}]
}
now I want to replace e
value with "example" in the above structure. Could some one help me.
I tried to loop through the json structure and was able to read the "e" value but can't replace it. I tried: `
std::vector<std::string> arr_value;
std::ifstream in("test.json");
json file = json::parse(in);
for (auto& td : file["b"])
for (auto& prop : td["d"])
arr_value.push_back(prop["e"]);
//std::cout<<"prop" <<prop["e"]<< std::endl;
for (const auto& x : arr_value)
std::cout <<"value in vector string= " <<x<< "\n";
for (decltype(arr_value.size()) i = 0; i <= arr_value.size() - 1; i++)
{
std::string s = arr_value[i]+ "emp";
std::cout <<"changed value= " <<s << std::endl;
json js ;
js = file;
std::ofstream out("test.json");
js["e"]= s;
out << std::setw(4) << js << std::endl;
}
The following appends MODIFIED
to every "e"-value and writes the result to test_out.json
:
#include <vector>
#include <iostream>
#include <fstream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main() {
std::ifstream in("test.json");
json file = json::parse(in);
for (auto& td : file["b"])
for (auto& prop : td["d"]) {
prop["e"] = prop["e"].get<std::string>() + std::string(" MODIFIED");
}
std::ofstream out("test_out.json");
out << std::setw(4) << file << std::endl;
}
The prop["e"] = ...
line does three things:
"e"
,.get<std::string>()
and appends "modified"
, andprop["e"]
, which is a reference to the object nested in the JSON structure.