nlohmann::basic_json::get_ref¶

template<typenameReferenceType>
ReferenceTypeget_ref();
template<typenameReferenceType>
constReferenceTypeget_ref()const;

Implicit reference access to the internally stored JSON value. No copies are made.

Template parameters¶

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.

Return value¶

reference to the internally stored JSON value if the requested reference type fits to the JSON value; throws type_error.303 otherwise

Exception safety¶

Strong exception safety: if an exception occurs, the original value stays intact.

Exceptions¶

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".

Complexity¶

Constant.

Notes¶

Undefined behavior

The reference becomes invalid if the underlying JSON object changes.

Examples¶

Example

The example shows several calls to get_ref().

#include<iostream>
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
intmain()
{
// create a JSON number
jsonvalue=17;
// explicitly getting references
autor1=value.get_ref<constjson::number_integer_t&>();
autor2=value.get_ref<json::number_integer_t&>();
// print the values
std::cout<<r1<<' '<<r2<<'\n';
// incompatible type throws exception
try
{
autor3=value.get_ref<json::number_float_t&>();
}
catch(constjson::type_error&ex)
{
std::cout<<ex.what()<<'\n';
}
}

Output:

1717
[json.exception.type_error.303]incompatibleReferenceTypeforget_ref,actualtypeisnumber

Version history¶

Added in version 1.1.0.
Extended to binary types in version 3.8.0.