= Value Conversion While the <<ref_value>> container makes it easy to create ad-hoc structures, often it is necessary to convert between JSON and user-defined types or types from the standard library.

The function template <<ref_value_from>> provides an interface to construct a <<ref_value>> from a type `T`. The function template <<ref_value_to>> converts in the opposite direction, from a type `T` to <<ref_value>>. Both support a wide variety of different https://en.cppreference.com/w/cpp/language/types[fundamental types], such as `int` or `double`, standard library types, such as `std::string` or `std::vector<T>`, and can be extended to support user-defined types.

Category of T

Comment

`value_from` behavior

`value_to` behavior

Boost.JSON container.

`bool`

https://en.cppreference.com/w/cpp/types/is_arithmetic[Arithmetic type]

The result is created via <<ref_value_to_number>>.

Type satisfying <<ref_is_string_like>>.

The result is a <<ref_string>>.

The result is constructed from a <<ref_string_view>>.

Type satisfying <<ref_is_variant_like>>.

The result is equal to the result of conversion of the active variant

alternative. |The result holds the first alternative for which a conversion succeeds.

Type satisfying <<ref_is_map_like>>.

A one-to-one mapping (e.g. `std::map`) with string-like keys.

The result is an <<ref_object>>.

The result is default-constructed, and elements are `insert`-ed at the end.