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json/doc/mkdocs/docs/api/basic_json/exception.md
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# <small>nlohmann::basic_json::</small>exception
```cpp
class exception : public std::exception;
```
This class is an extension of [`std::exception`](https://en.cppreference.com/w/cpp/error/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.
```plantuml
std::exception <|-- basic_json::exception
basic_json::exception <|-- basic_json::parse_error
basic_json::exception <|-- basic_json::invalid_iterator
basic_json::exception <|-- basic_json::type_error
basic_json::exception <|-- basic_json::out_of_range
basic_json::exception <|-- basic_json::other_error
interface std::exception {}
class basic_json::exception #FFFF00 {
+ const int id
+ const char* what() const
}
class basic_json::parse_error {
+ const std::size_t byte
}
```
Subclasses:
- [`parse_error`](parse_error.md) for exceptions indicating a parse error
- [`invalid_iterator`](invalid_iterator.md) for exceptions indicating errors with iterators
- [`type_error`](type_error.md) for exceptions indicating executing a member function with a wrong type
- [`out_of_range`](out_of_range.md) for exceptions indicating access out of the defined range
- [`other_error`](other_error.md) 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
??? example
The following code shows how arbitrary library exceptions can be caught.
```cpp
--8<-- "examples/exception.cpp"
```
Output:
```json
--8<-- "examples/exception.output"
```
## See also
[List of exceptions](127.0.0.1:8000/home/exceptions/)
## Version history
- Since version 3.0.0.