Poco Iterating Nested JSON Objects

Question

I have a JSON with nested objects (here is a made up example as the real json is bigger and complex). I need to Iterate through siblings object. I know how to do it with array but could not find any example to deal with such nested object (of any nesting depth).

Any idea is appreciated.

{
    .......
    "siblings":{
        "Michael":{
            "age":20,
            "lives":"Dodoma"
        },
        "Polyasi":{
            "age":25,
            "lives":"Geita"
        },
        "Kiah":{
            "age":3,
            "lives":"Dar es Salaam"
        }
    }
    ...........
}

Look at the documentation for Object. It looks the same as iterating over a std::map. — Alex
– Alex, Commented Jul 11, 2017 at 21:19
I assume you refer to ValueMap::iterator. AFAIK, it is for values. Now I'm not sure if that covers Objects like in my case and the way to convert the value to Poco::JSON::Object. — Stefano Mtangoo
– Stefano Mtangoo, Commented Jul 11, 2017 at 21:54
I guess would be better posted complete example with input json and expected result. — user4651282
– user4651282, Commented Jul 11, 2017 at 22:24
complete json is here packagist.org/packages/yiisoft/yii2.json the results I expect is reading versions. I can already read everything except nested json. Am going to try the idea of Value Map iterator and see how it is gong to work out — Stefano Mtangoo
– Stefano Mtangoo, Commented Jul 12, 2017 at 4:32

Stefano Mtangoo · Accepted Answer · 2017-07-12 05:28:36Z

So I found that ValueMap::Iterator does not care whether it is an Object or atomic values it treats them the same. So here is an example that I coined to actually test this. Thanks to @atomic_alarm for pushing me into testing something I had given up as potential solution.

the packagist.json is actually renamed JSON file found here. Here is the code. Make sure that you link against foundation and json libraries.

#include <Poco/JSON/Parser.h>
#include <Poco/Dynamic/Var.h>
#include <string>
#include <fstream>
#include <streambuf>
#include <iostream>

void print_version_names(Poco::JSON::Object::Ptr root);

int main(int argc, char** argv)
{
    //read file
    std::ifstream t("packagist.json");
    std::string json_str((std::istreambuf_iterator<char>(t)),
                 std::istreambuf_iterator<char>());

    Poco::JSON::Parser parser;
    Poco::Dynamic::Var result = parser.parse(json_str);
    Poco::JSON::Object::Ptr json = result.extract<Poco::JSON::Object::Ptr>();

    print_version_names(json);

    return 0;
}

void print_version_names(Poco::JSON::Object::Ptr root)
{
    std::string root_key = "package";
    std::string key = "versions";
    //no checks whether such key acually exists
    Poco::JSON::Object::Ptr package_json = root->getObject(root_key);
    //get the nested objects
    Poco::JSON::Object::Ptr nested_versions = package_json->getObject(key);

    //iterate the map
    Poco::JSON::Object::Iterator it;
    for(it = nested_versions->begin(); it != nested_versions->end(); it++)
    {
        //no check of whether it is an object
        std::cout<<it->first<<"\n";
    }
}

Results:

2.0.0
2.0.0-alpha
2.0.0-beta
2.0.0-rc
2.0.1
2.0.10
2.0.11
2.0.11.1
2.0.11.2
2.0.12
2.0.2
2.0.3
2.0.4
2.0.5
2.0.6
2.0.7
2.0.8
2.0.9

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