nlohmann::basic_json::exception¶

classexception:publicstd::exception;

This class is an extension of std::exception objects with a member id for exception ids. It is used as the base class for all exceptions thrown by the basic_json class. This class can hence be used as "wildcard" to catch exceptions, see example below.

classDiagram
 direction LR
 class std_exception ["std::exception"] {
 <<interface>>
 }
 class json_exception ["basic_json::exception"] {
 +const int id
 +const char* what() const
 }
 class json_parse_error ["basic_json::parse_error"] {
 +const std::size_t byte
 }
 class json_invalid_iterator ["basic_json::invalid_iterator"]
 class json_type_error ["basic_json::type_error"]
 class json_out_of_range ["basic_json::out_of_range"]
 class json_other_error ["basic_json::other_error"]
 std_exception <|-- json_exception
 json_exception <|-- json_parse_error
 json_exception <|-- json_invalid_iterator
 json_exception <|-- json_type_error
 json_exception <|-- json_out_of_range
 json_exception <|-- json_other_error
 style json_exception fill:#CCCCFF

Subclasses:

• parse_error for exceptions indicating a parse error
• invalid_iterator for exceptions indicating errors with iterators
• type_error for exceptions indicating executing a member function with a wrong type
• out_of_range for exceptions indicating access out of the defined range
• other_error for exceptions indicating other library errors

Member functions¶

• what - returns explanatory string

Member variables¶

• id - the id of the exception

Notes¶

To have nothrow-copy-constructible exceptions, we internally use std::runtime_error which can cope with arbitrary-length error messages. Intermediate strings are built with static functions and then passed to the actual constructor.

Examples¶

#include<iostream>
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
intmain()
{
try
{
// calling at() for a non-existing key
jsonj={{"foo","bar"}};
jsonk=j.at("non-existing");
}
catch(constjson::exception&e)
{
// output exception information
std::cout<<"message: "<<e.what()<<'\n'
<<"exception id: "<<e.id<<std::endl;
}
}

message:[json.exception.out_of_range.403]key'non-existing'notfound
exceptionid:403

See also¶

List of exceptions

Version history¶

• Since version 3.0.0.