template<typename ReferenceType> ReferenceType get_ref(); template<typename ReferenceType> const ReferenceType get_ref() const;
Implicit reference access to the internally stored JSON value. No copies are made.
ReferenceType : reference type; must be a reference to array_t, object_t, string_t, boolean_t, number_integer_t, or number_unsigned_t, number_float_t, or binary_t. Enforced by a static assertion.
reference to the internally stored JSON value if the requested reference type fits to the JSON value; throws type_error.303 otherwise
Strong exception safety: if an exception occurs, the original value stays intact.
Throws type_error.303 if the requested reference type does not match the stored JSON value type; example: "incompatible ReferenceType for get_ref, actual type is binary".
Constant.
Undefined behavior
The reference becomes invalid if the underlying JSON object changes.
Example
The example shows several calls to get_ref().
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create a JSON number
json value = 17;
// explicitly getting references
auto r1 = value.get_ref<const json::number_integer_t&>();
auto r2 = value.get_ref<json::number_integer_t&>();
// print the values
std::cout << r1 << ' ' << r2 << '\n';
// incompatible type throws exception
try
{
auto r3 = value.get_ref<json::number_float_t&>();
}
catch (const json::type_error& ex)
{
std::cout << ex.what() << '\n';
}
}
Output:
17 17 [json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is number