null check for operator[] for const json object

[Wokarol]

I was trying to write something like this:

const json& foo = data["foo"];
if (!foo.is_null())
{
  ...
}

Where data would also be const json&

This works well for non-const objects, but in this case it leads to abort. Is there any good solution for that?

[nlohmann]

Use at() or contains().

[Wokarol]

But using .contains() requires basically two searches in the json file and .at() requires exceptions. Both of which aren't ideal

[nlohmann]

See https://json.nlohmann.me/features/element_access/unchecked_access/ for the rationale. Alternatively, use find().

[jjcasmar]

I sometimes use data.value("foo", json()); and can check for null as you do

[nlohmann]

You could also use find and check the returned iterator.