Request: range-based-for over a json-object to expose .first/.second

[jaredgrubb]

I would love to have the ability to iterate over a JSON object type in exactly the same way I would iterate over a std::map:

for(auto& i : map) { i.first; i.second; }

Would it be possible to have a free function (or member) that would allow me to do something like:
for(auto& i : as_map(jsonObj)) {...}
such that the iterator exposed here works more like map::iterator (.first,.second) than the current iterator type (.key,.value).

[nlohmann]

I did not find a way to realize this without any syntactic adjustment, but you can do this:

json j = {{"A", 1}, {"B", 2}};

for (auto i : json::iterator_wrapper(j))
{
  auto x = i.key(); // x = "A", x = "B"
  auto y = i.value(); // y = 1, y = 2
}

See https://github.com/nlohmann/json/blob/develop/test/src/unit-iterator_wrapper.cpp for more examples.

If you have any idea to realize this without a wrapper, please let me know!

[jaredgrubb]

I think it will require:

• a wrapper function
• a new iterator type (whose value type is pair<string,json> instead of key/value).

Personally, I really dont like the key/value functions and would rather just use first/second ... and this is the minimal approach I can think of. What do you think? I'm happy to start working on a patch, but if you think it's a non-starter, then I'll skip it.

[nlohmann]

So basically the syntax of the loop would be the same, but you'd rather write i.first than i.key()?

[jaredgrubb]

My goal is to make range-for over a json-object easy, which really doesnt work right now (well without your "iterator_wrapper" suggestion, which is not very discoverable). I personally prefer .first/.second because I want it to feel like a map, but that's bikeshedding.

Honestly, none of these sound like awesome solutions. Another option is to use get_ref to get the internal STL map object, but that's even worse to type.

[nlohmann]

So again - if there would be a better name for the iteration_wrapper (maybe also a more prominent documentation), and additional first/second members - would you see this as an improvement? Any name suggestions?

[nlohmann]

Any opinions on this?

[nlohmann]

I once again shall try to get another opinion on how to name the iteration_wrapper...

[jaredgrubb]

make_iterator(json&)?

[jaredgrubb]

make_object_iterator(json&)?