Print JSON with matching key - RapidJSON

Question

I'm trying to print from a JSON only the values that matching some keys:

#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>

using namespace rapidjson;

char* kTypeNames[] = { "First", "text", "print", "key" };

int main() {
// 1. Parse a JSON string into DOM.
const char json[] =
" { \"First\" : \"a\", \"text\" : \"b\" ,\"key\" : \"hello\" ,
\"print\" : \"1\",\"print\" : \"2\",\"no_key\" : \"2\"} ";
// ...
Document document;
document.Parse(json);

printf(json);

printf("\nAccess values in document:\n");
assert(document.IsObject());

for (Value::ConstMemberIterator itr = document.MemberBegin();
itr !=document.MemberEnd(); ++itr)
{
    //how to print element that matches with kTypeNames array?
}
}

Keys needed are First, text, print and key, and I want to ignore no_key value. So I want to print only a, b, hello, 1 and do not print 2.

I'm looking and the documentation trying to find out how to do it.

Thanks

Answer 1

You don't need to iterate each member and see if it matches in the 'key' list. Rather use document.HasMember() to see if the key exists.

#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>

using namespace rapidjson;

const char* kTypeNames[] = { "First", "text", "print", "key" };

int main() {
    // 1. Parse a JSON string into DOM.
    const char json[] =
        " { \"First\" : \"a\", \"text\" : \"b\" ,\"key\" : \"hello\" ,\"print\" : \"1\",\"print\" : \"2\",\"no_key\" : \"2\"} ";
    // ...
    Document document;
    document.Parse(json);

    printf(json);

    printf("\nAccess values in document:\n");
    assert(document.IsObject());

  //For each type in ktypenames, see if json has member

    for (auto Typename : kTypeNames) {
        if (document.HasMember(Typename)) {
            std::cout << Typename << ":" << document[Typename].GetString() << std::endl;
        }

    }
}