c++ rapidjson get add value to exist array

Question

I tried to create a class which will add a value to a Json array. I tried to do it like this:

void functions::Json::SetArray(rapidjson::Document &JsonObj, std::string ArrayName, std::string value)
{
        if (!JsonObj.IsObject()) 
        JsonObj.SetObject();
    

    rapidjson::Document::AllocatorType& alloc = JsonObj.GetAllocator();
    
    rapidjson::Value KeyPart;
    KeyPart.SetString(ArrayName.c_str(), alloc);

    rapidjson::Value ValuePart;
    ValuePart.SetString(value.c_str(), alloc);

    rapidjson::Value array(rapidjson::kArrayType);
    
    
    if (!JsonObj["array"].IsNull())
        array = JsonObj["array"];
        

    array.PushBack(ValuePart, alloc);
    JsonObj.AddMember(KeyPart, array, alloc);

}

But I have an error:

rapidjson/document.h:1218: rapidjson::GenericValue<Encoding,
Allocator>& rapidjson::GenericValue<Encoding,
Allocator>::operator[](const rapidjson::GenericValue<Encoding,
SourceAllocator>&) [with SourceAllocator =
rapidjson::MemoryPoolAllocator<rapidjson::CrtAllocator>; Encoding =
rapidjson::UTF8<>; Allocator =
rapidjson::MemoryPoolAllocator<rapidjson::CrtAllocator>]: Assertion
`false' failed.

How do I correctly do it?

Answer 1

Taking a look at rapidjson/document.h:1218, this appears to be how it errors when you use the [] operator with a member that doesn't exist, probably where you access JsonObj["array"].

If I use MemberFind to look up the member first, it works fine for me:

rapidjson::Document::MemberIterator existingArray = JsonObj.FindMember("array");
if (existingArray != JsonObj.MemberEnd() && !existingArray->value.IsNull())
    array = existingArray->value;