write json

pcln("add a value into array");

    Value item(Type::kObjectType);
    item.AddMember("key", "word5", doc.GetAllocator());
    item.AddMember("value", "单词5", doc.GetAllocator());
    contents.PushBack(item, doc.GetAllocator());

    // convert dom to string.
    StringBuffer buffer; // in rapidjson/stringbuffer.h
    Writer<StringBuffer> writer(buffer); // in rapidjson/writer.h
    doc.Accept(writer);

    psln(buffer.GetString());