value::at (3 of 6 overloads)

Access an element, with bounds checking.

value const&
at(
    string_view key,
    boost::source_location const& loc = BOOST_CURRENT_LOCATION) const&;

This function is used to access elements of the underlying object, or throw an exception if the value is not an object.

Constant.

Strong guarantee.

Name	Description
`key`	The key of the element to find.
`loc`	`source_location` to use in thrown exception; the source location of the call site by default.

this->as_object(loc).at( key, loc ).