Read a sub json using boost property tree - c++

Question

I need to read a field in a JSON file which itself is a JSON. I need to read the JSON field in one go. Is there any way available? Sample JSON I am trying to read is provided below.
enter code here
{
"responses": [
{
"id": "1",
"status": 200,
"headers": {
"OData-Version": "4.0",
"Content-Type":"application/json;odata.metadata=minimal;odata.streaming=true"
},
"body": {
"createdDateTime": "2021-04-22T09:24:59.394Z",
"displayName": "Test1",
"visibility": "public",
"isMembershipLimitedToOwners": false,
"discoverySettings": { "showInTeamsSearchAndSuggestions": true },
"memberSettings": {
"allowCreateUpdateChannels": true,
"allowCreateUpdateRemoveConnectors": true
},
"guestSettings": {
"allowCreateUpdateChannels": true,
"allowDeleteChannels": false
},
"messagingSettings": {
"allowUserEditMessages": true,
"allowChannelMentions": true
},
"funSettings": {
"allowGiphy": true,
"allowCustomMemes": true
}
} } ]
}
I am trying to read the "body" field using the code below (json is read in boost::property_tree::ptree jsonBatchResponse jsonBatchResponse). But strBody is empty and it doesn't read the "Body" field correctly. :
enter code here
for (auto& v : jsonBatchResponse.get_child("responses"))
{
std::string strID = v.second.get<std::string>("id", "");
std::string strStatus = v.second.get<std::string>("status", "");
std::string strBody = v.second.get<std::string>("body", "");
}
It looks like v.second.getstd::string("body", "") is not the right way to read the JSON field. Is there any other way available (other than reading individual fields in the JSON value)? Please let me know.

Answer 1

The body is not a string.
So, getting the child object would be in order:
for (auto const& v : jsonBatchResponse.get_child("responses")) {
std::string strID = v.second.get<std::string>("id", "");
std::string strStatus = v.second.get<std::string>("status", "");
ptree const& body = v.second.get_child("body");
}
If you add some output to that loop with e.g.
std::cout << std::quoted(strID) << "\n";
std::cout << std::quoted(strStatus) << "\n";
write_json(std::cout, body);
It will print Live On Coliru
"1"
"200"
{
"createdDateTime": "2021-04-22T09:24:59.394Z",
"displayName": "Test1",
"visibility": "public",
"isMembershipLimitedToOwners": "false",
"discoverySettings": {
"showInTeamsSearchAndSuggestions": "true"
},
"memberSettings": {
"allowCreateUpdateChannels": "true",
"allowCreateUpdateRemoveConnectors": "true"
},
"guestSettings": {
"allowCreateUpdateChannels": "true",
"allowDeleteChannels": "false"
},
"messagingSettings": {
"allowUserEditMessages": "true",
"allowChannelMentions": "true"
},
"funSettings": {
"allowGiphy": "true",
"allowCustomMemes": "true"
}
}
BONUS: Using a proper JSON library instead
Boost Property Tree is NOT a JSON library, and therefore has a lot of limitations.
Instead I suggest using Boost JSON:
Live On Coliru
#include <boost/json.hpp>
#include <boost/json/src.hpp>
#include <iostream>
namespace json = boost::json;
extern std::string sample;
int main() {
json::object jsonBatchResponse = json::parse(sample).as_object();
for (auto& v : jsonBatchResponse["responses"].as_array()) {
auto& res = v.as_object();
json::value id = res["id"], // string
status = res["status"], // integer
body = res["body"]; // object
std::cout << id << "\n";
std::cout << status << "\n";
std::cout << body << "\n";
}
}
std::string sample = R"(
{
"responses": [{
"id": "1",
"status": 200,
"headers": {
"OData-Version": "4.0",
"Content-Type": "application/json;odata.metadata=minimal;odata.streaming=true"
},
"body": {
"createdDateTime": "2021-04-22T09:24:59.394Z",
"displayName": "Test1",
"visibility": "public",
"isMembershipLimitedToOwners": false,
"discoverySettings": {
"showInTeamsSearchAndSuggestions": true
},
"memberSettings": {
"allowCreateUpdateChannels": true,
"allowCreateUpdateRemoveConnectors": true
},
"guestSettings": {
"allowCreateUpdateChannels": true,
"allowDeleteChannels": false
},
"messagingSettings": {
"allowUserEditMessages": true,
"allowChannelMentions": true
},
"funSettings": {
"allowGiphy": true,
"allowCustomMemes": true
}
}
}]
}
)";
Prints
"1"
200
{"createdDateTime":"2021-04-22T09:24:59.394Z","displayName":"Test1","visibility":"public","isMembershipLimitedToOwners":false,"discoverySettings":{"showInTeamsSearchAndSuggestions":true},"memberSettings":{"allowCreateUpdateChannels":true,"allowCreateUpdateRemoveConnectors":true},"guestSettings":{"allowCreateUpdateChannels":true,"allowDeleteChannels":false},"messagingSettings":{"allowUserEditMessages":true,"allowChannelMentions":true},"funSettings":{"allowGiphy":true,"allowCustomMemes":true}}