Where is get(key, default)?

[gatopeich]

Improvement

The library would be more usable if it offered get(key, default=null) interface.

Why

A great feature of this library is bringing the power of Python/Javascript objects to C++.

Only it lacks object.get(key, default=null) interface, which is such an useful feature!

Turns out that the functionality is actually there, but the choice of name "value" is not adequate. It takes a bit of research to find, actually I thought it was not there for a while and had to implement it myself.

It also happens that the semantics of "get" and "value" are swapped: each one means what the other says!

Since swapping "get()" with "value()" would break existing code, I hereby propose to make them work both ways:

• get(key, default) == value(key, default)
• value() == get()

Please describe the steps to reproduce the issue.

1. Start using this great library
2. Where is object.get(key, default) ???
3. Can't find it, end up writing object.contains(key) ? object[key] : default

[nlohmann]

I don't think changing the names is a good idea now, as it would be a breaking change and probably add more confusion than resolving it.

However, this is the rationale for the names:

• T basic_json::get<T>() was motivated by the std::get function from std::variant or std::tuple. You provide a type and you get the value.
• That name gone, we had to find something else for "give me an object value with a default value". Hence value.

Sorry for the inconvenience.

[gatopeich]

Thanks for the rationale.

Still I see no conflict with having an overload T basic_json::get<T>(KeyT key, T default=null) const.

Is it as hard as an ordered_json? 🙂

[nlohmann]

Having two functions doing the same thing would be even more confusing.

[gatopeich]

Maybe, for maintainers.

The confusion for users arises from not finding "get(key)" in the first place.

If the reason to have "value" was that "get" was gone, there is no reason.

[cxwx]

still no get（key） function for default value？

[nlohmann]

It's called value.

[cxwx]

thanks

[cxwx]

@nlohmann
if I have an array

{"source":
[
{"a":“string”},
{"a":null},
...
]
}

I'd love to use a for cycle

for (auto i : json["source"]) {
if(json.at("a").is_null()){ // how can I remove this line?
...
}
else
{
int k = json.value("a", “-1”);
}
}

Can I set the null as default value?