How to read Json string starting with square brackets in it? [duplicate] - c++

Question

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How to use boost::property_tree to parse JSON with array root
(1 answer)
Closed 2 years ago.
I am using c++ code to read json string to retrieve value based on specific key names. Example of my json response from web API is in array format like below.
[
{
"username": "123456",
"useraddress": "abc",
"data": [
{
"schedule": true,
"task": "abc",
"risk": "1",
}
],
"date": "0000-00-00"
}
]
Like the above format is the actual response. I have to retrieve date value using key "date".
My code snippet:
{
std::stringstream jsonString;
boost::property_tree::ptree pt;
jsonString << ws2s(Info).c_str();
boost::property_tree::read_json(jsonString, pt);
std::string date = pt.get<std::string>("date");
}
'Info' in above snippet is wsstring containing json response data.
I can able to retrieve "date" if [] square brackets are removed manually. Since it is array format, if I pass without removing brackets, read_json throws error.
Can somebody help this out?

Answer 1

Yeah. Boost Property Tree is a property tree library, not JSON.
You're in luck though, Boost has a JSON library now https://www.boost.org/doc/libs/1_75_0/libs/json/doc/html/index.html
Note: your input isn't valid JSON either, because JSON doesn't strictly allow trailing commas. You can enable them with an option in Boost JSON though:
Live On Compiler Explorer
#include <boost/json.hpp>
#include <iostream>
int main() {
std::string input = R"(
[
{
"username": "123456",
"useraddress": "abc",
"data": [
{
"schedule": true,
"task": "abc",
"risk": "1",
}
],
"date": "0000-00-00"
}
])";
boost::json::parse_options options;
options.allow_trailing_commas = true;
auto json = boost::json::parse(input, {}, options);
for (auto& el : json.as_array()) {
std::cout << el.at("date") << "\n";
}
}
Prints
"0000-00-00"