How to use a json::iterator dereferenced value in code?

[014972304505347]

I am trying to do something like this - it involves taking a json::iterator through some json objects, and getting their keys and values for entries. I want to use the values (i.e. it.value() and mit.value()) as arguments to other functions...

    json result;
    json inboundMessage = ...;//determined at runtime
    json savedMessage = ...; //determined at runtime
    for (json::iterator it = inboundMessage.begin(), mit = savedMessage.begin(); it != inboundMessage.end() && mit != savedMessage.end(); ++it, ++mit) {
	json pair;
	pair.emplace_back("log", it.value());
        pair.emplace_back("data", mit.value());
	result.emplace_back(it.key(), pair);
    }
    return result;

When I build, I get the following error:
'nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer>::basic_json(nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer> &&) noexcept': cannot convert argument 1 from 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' to 'std::initializer_list<nlohmann::detail::json_ref<nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer>>>'

What is the correct way to access the value referenced by an iterator such that the value can be used by code?

[gregmarr]

You want to use json.items() and not the json object itself for iteration.

auto inbound = inboundMessage.items();
auto saved = savedMessage.items();

for (auto it = inbound.begin(), ...

[014972304505347]

I still get the same error when I do that...

[gregmarr]

Which line is giving you the error?

[014972304505347]

These three lines seem to trigger it individually, triggering 3 errors in total:

     pair.emplace_back("log", it.value());
     pair.emplace_back("data", mit.value());
     result.emplace_back(it.key(), pair);

Actually, the error is technically at line 920 in file "xmemory0". The line is in this block ( I commented on the line with the error) :

template<class _Objty,
	class... _Types>
	static void construct(_Alloc&, _Objty * const _Ptr, _Types&&... _Args)
	{	// construct _Objty(_Types...) at _Ptr
	::new (const_cast<void *>(static_cast<const volatile void *>(_Ptr)))
		_Objty(_STD forward<_Types>(_Args)...); //**THE ERROR IS ON THIS LINE**
	}

File "xmemory0" is located at
C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.14.26428\include

for me and is of type "FILE" (no extension...).

[gregmarr]

Ah, you're inserting in a map, you want emplace, not emplace_back. The latter is only for arrays.

[014972304505347]

That solved it. Thank you!

I wonder if its possible to throw better errors in a situation like this. It was not obvious to me that something like this could be the issue, and I thought the error was something else entirely...

[gregmarr]

I don't think it's possible, as the error is that by using emplace_back you're essentially passing these parameters to the constructor of a json object through std::vector<json>::emplace_back().