std::bad_optional_access - cppreference.com (original) (raw)

Defines a type of object to be thrown by std::optional::value when accessing an optional object that does not contain a value.

Inheritance diagram

Contents

• 1 Member functions
• 2 std::bad_optional_access::bad_optional_access
  • 2.1 Parameters
• 3 std::bad_optional_access::operator=
  • 3.1 Parameters
  • 3.2 Return value
• 4 std::bad_optional_access::what
  • 4.1 Return value
  • 4.2 Notes
• 5 Inherited from std::exception
  • 5.1 Member functions
  • 5.2 Notes
  • 5.3 Example
  • 5.4 See also

[edit] Member functions

| | constructs a new bad_optional_access object (public member function) | | ------------------------------------------------------------------------- | | | replaces the bad_optional_access object (public member function) | | | returns the explanatory string (public member function) |

std::bad_optional_access::bad_optional_access

Constructs a new bad_optional_access object with an implementation-defined null-terminated byte string which is accessible through what().

1. Default constructor.

2. Copy constructor. If *this and other both have dynamic type std::bad_optional_access then std::strcmp(what(), other.what()) == 0.

Parameters

std::bad_optional_access::operator=

| bad_optional_access& operator=( const bad_optional_access& other ) noexcept; | | (since C++17) (constexpr since C++26) | | --------------------------------------------------------------------------------- | | ------------------------------------- |

Assigns the contents with those of other. If *this and other both have dynamic type std::bad_optional_access then std::strcmp(what(), other.what()) == 0 after assignment.

Parameters

Return value

*this

std::bad_optional_access::what

| virtual const char* what() const noexcept; | | (since C++17) (constexpr since C++26) | | ------------------------------------------- | | ------------------------------------- |

Returns the explanatory string.

Return value

Pointer to an implementation-defined null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring. The pointer is guaranteed to be valid at least until the exception object from which it is obtained is destroyed, or until a non-const member function (e.g. copy assignment operator) on the exception object is called.

Notes

Implementations are allowed but not required to override what().

Inherited from std::exception

Member functions

| | destroys the exception object (virtual public member function of std::exception) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | returns an explanatory string (virtual public member function of std::exception) [edit] |

[edit] Notes

[edit] Example

#include #include   int main() { std::optional opt; // creates an empty optional try { [[maybe_unused]] auto x = opt.value(); // throws } catch (const std::bad_optional_access& ex) { std::cout << ex.what() << '\n'; } }

Possible output:

[edit] See also