Boost C++ Libraries

Convert an object of type T to value.

Synopsis

Defined in header <boost/json/value_from.hpp>

template<
    class T,
    class Context>
void
value_from(
    T&& t,
    Context const& ctx,
    value& jv);

Description

This function attempts to convert an object of type T to value using

Out of the box the function supports types satisfying SequenceContainer, arrays, arithmetic types, bool, std::tuple, std::pair, std::variant, std::optional, std::monostate, and std::nullopt_t. Conversion of other types is done by calling an overload of tag_invoke found by argument-dependent lookup. Its signature should be similar to:

template < class FullContext >
void tag_invoke( value_from_tag, value&, T,  const Context& , const FullContext& );

or

void tag_invoke( value_from_tag, value&, T,  const Context& );

or

void tag_invoke( value_from_tag, value&, T );

The overloads are checked for existence in that order and the first that matches will be selected.

The ctx argument can be used either as a tag type to provide conversions for third-party types, or to pass extra data to the conversion function.

Exception Safety

Strong guarantee.

Template Parameters

Parameters

See Also

value_from_tag, value_to, tag_invoke: A general pattern for supporting customisable functions

Convenience header <boost/json.hpp>