JSON for Modern C++  3.6.1

◆ type_error

template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
using nlohmann::basic_json::type_error = detail::type_error

This exception is thrown in case of a type error; that is, a library function is executed on a JSON value whose type does not match the expected semantics.

Exceptions have ids 3xx.

name / id example message description
json.exception.type_error.301 cannot create object from initializer list To create an object from an initializer list, the initializer list must consist only of a list of pairs whose first element is a string. When this constraint is violated, an array is created instead.
json.exception.type_error.302 type must be object, but is array During implicit or explicit value conversion, the JSON type must be compatible to the target type. For instance, a JSON string can only be converted into string types, but not into numbers or boolean types.
json.exception.type_error.303 incompatible ReferenceType for get_ref, actual type is object To retrieve a reference to a value stored in a basic_json object with get_ref, the type of the reference must match the value type. For instance, for a JSON array, the ReferenceType must be array_t &.
json.exception.type_error.304 cannot use at() with string The at() member functions can only be executed for certain JSON types.
json.exception.type_error.305 cannot use operator[] with string The operator[] member functions can only be executed for certain JSON types.
json.exception.type_error.306 cannot use value() with string The value() member functions can only be executed for certain JSON types.
json.exception.type_error.307 cannot use erase() with string The erase() member functions can only be executed for certain JSON types.
json.exception.type_error.308 cannot use push_back() with string The push_back() and operator+= member functions can only be executed for certain JSON types.
json.exception.type_error.309 cannot use insert() with The insert() member functions can only be executed for certain JSON types.
json.exception.type_error.310 cannot use swap() with number The swap() member functions can only be executed for certain JSON types.
json.exception.type_error.311 cannot use emplace_back() with string The emplace_back() member function can only be executed for certain JSON types.
json.exception.type_error.312 cannot use update() with string The update() member functions can only be executed for certain JSON types.
json.exception.type_error.313 invalid value to unflatten The unflatten function converts an object whose keys are JSON Pointers back into an arbitrary nested JSON value. The JSON Pointers must not overlap, because then the resulting value would not be well defined.
json.exception.type_error.314 only objects can be unflattened The unflatten function only works for an object whose keys are JSON Pointers.
json.exception.type_error.315 values in object must be primitive The unflatten function only works for an object whose keys are JSON Pointers and whose values are primitive.
json.exception.type_error.316 invalid UTF-8 byte at index 10: 0x7E The dump function only works with UTF-8 encoded strings; that is, if you assign a std::string to a JSON value, make sure it is UTF-8 encoded.
json.exception.type_error.317 JSON value cannot be serialized to requested format The dynamic type of the object cannot be represented in the requested serialization format (e.g. a raw true or null JSON object cannot be serialized to BSON)
Example
The following code shows how a type_error exception can be caught.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  try
9  {
10  // calling push_back() on a string value
11  json j = "string";
12  j.push_back("another string");
13  }
14  catch (json::type_error& e)
15  {
16  // output exception information
17  std::cout << "message: " << e.what() << '\n'
18  << "exception id: " << e.id << std::endl;
19  }
20 }
basic_json<> json
default JSON class
Definition: json.hpp:871
detail::type_error type_error
exception indicating executing a member function with a wrong type
Definition: json.hpp:13002

Output (play with this example online):
message: [json.exception.type_error.308] cannot use push_back() with string
exception id: 308
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/type_error.cpp -o type_error 
See also
- exception for the base class of the library exceptions
- parse_error for exceptions indicating a parse error
- invalid_iterator for exceptions indicating errors with iterators
- out_of_range for exceptions indicating access out of the defined range
- other_error for exceptions indicating other library errors
Since
version 3.0.0

Definition at line 13002 of file json.hpp.