Using jsoncpp::fields() out of struct

[niXman]

Hi,

Tell me please, how can I use jsoncpp::fields() out of struct?
For example I have a string with JSON and I want to get the fields from this JSON.

int a, b;
std::string str = R"({"a":1,"b":2})";
jsoncpp::fields(str, "a", a, "b", b);

How can I do this?

Thanks.

[ascheglov]

You can't, not yet.
The fields function has a static local variable inside, so if you write

int a, x;
fields("{'a':1}", "a", a);
fields("{'x':2}", "x", x);

It won't parse x because compiler already initialized that variable for "a".
Hence the Cls& parameter, which acts as a tag and makes compiler generate separate specializations for fields.

With constexpr magic it's possible to get rid of that cls parameter.

[niXman]

thanks, closed.