sen::Result< T, E > Class Template Reference

Result<T, E> is a template type that can be used to return and propagate errors. The intent is to replace exceptions in this context. Result<T, E> is an algebraic data type of Ok(T) that represents success and Err(E) representing an error. More...

#include <result.h>

Public Types
using	ValueType = T
using	ErrorType = E

Public Member Functions
	Result (impl::Ok< T > &&ok) noexcept
	Construct a Result that indicates success and that carries a valid return value.
	Result (impl::Err< E > &&err) noexcept
	Construct a Result that indicates failure and that carries an error value.
	~Result ()=default
template<typename U, typename G, std::enable_if_t< std::conjunction_v< std::is_constructible< T, const U & >, std::is_constructible< E, const G & > >, bool > = true>
	Result (const Result< U, G > &other)
	Do a conversion construction from a compatible Result.
template<typename U, typename G, std::enable_if_t< std::conjunction_v< std::is_constructible< T, U >, std::is_constructible< E, G > >, bool > = true>
	Result (Result< U, G > &&other)
	Do a conversion construction from a compatible Result.
bool	operator== (const Result &other) const
bool	operator!= (const Result &other) const
bool	isOk () const noexcept
	Used to determine if the result is not an error.
bool	isError () const noexcept
	Used to determine if the result is an error.
	operator bool () const noexcept
	Used to determine if the result is not an error.
template<typename U = T>
const impl::NonVoidT< U > &	getValueOr (const U &defaultVal) const noexcept
	Used to determine the return value. If the result indicates an error this method will return defaultValue.
template<typename U = T>
const impl::NonVoidT< U > &	getValue () const &
	Used to determine the success value, given that there is no error.
template<typename U = T>
impl::NonVoidT< U > &&	getValue () &&
	Used to move out the success value, given that there is no error.
const E &	getError () const
	Used to determine the error value, given that there is an error.
template<typename U = T>
const impl::NonVoidT< U > &	expect (std::string_view errorMsg={}) const noexcept
	Extracts the value of the correct result, or terminates the program with a given error message.

Detailed Description

template<typename T, typename E>
class sen::Result< T, E >

Result<T, E> is a template type that can be used to return and propagate errors. The intent is to replace exceptions in this context. Result<T, E> is an algebraic data type of Ok(T) that represents success and Err(E) representing an error.

Design of this class has been mainly inspired by Rust's std::result. Example:

enum class ErrorCode { too_small, too_large };
 
Result<int, ErrorCode> doSomething(int a) noexcept
{
  if (a < 0)
  {
    return Err(ErrorCode::too_small);
  }
  return Ok(a + 100);
}
 
Result<void, ErrorCode> doSomethingElse(int a) noexcept
{
  if (a < 0)
  {
    return Err(ErrorCode::too_small);
  }
  return Ok();
}

Use isOk(), isError() or the bool() operator to check if there was an error. Use getError() to get the error data (terminates the program if there was no error). Use getValue() to determine the return value if there is no error (terminates the program otherwise). Use getValueOr(X) as getValue() but returns X if there was an error.

Example:

if (auto result = doSomething())       // result cannot be ignored (would not compile)
{
  const auto& val = result.getValue(); // do something with val, if there is any
}                                      // (getValue is not present when T is 'void')
else
{
  auto err = result.getError();        // do something with err
}

Note

This class is not thread-aware.

Template Parameters

T	the type of the result if there is no error (can be void).
E	the type of the error.

Member Typedef Documentation

ValueType

template<typename T, typename E>

using sen::Result< T, E >::ValueType = T

ErrorType

template<typename T, typename E>

using sen::Result< T, E >::ErrorType = E

Constructor & Destructor Documentation

Result() [1/4]

template<typename T, typename E>

sen::Result< T, E >::Result ( impl::Ok< T > && ok )

inlinenoexcept

Construct a Result that indicates success and that carries a valid return value.

Result() [2/4]

template<typename T, typename E>

sen::Result< T, E >::Result ( impl::Err< E > && err )

inlinenoexcept

Construct a Result that indicates failure and that carries an error value.

~Result()

template<typename T, typename E>

sen::Result< T, E >::~Result ( )

default

Result() [3/4]

template<typename T, typename E>

template<typename U, typename G, std::enable_if_t< std::conjunction_v< std::is_constructible< T, const U & >, std::is_constructible< E, const G & > >, bool > = true>

sen::Result< T, E >::Result ( const Result< U, G > & other )

inline

Do a conversion construction from a compatible Result.

Result() [4/4]

template<typename T, typename E>

template<typename U, typename G, std::enable_if_t< std::conjunction_v< std::is_constructible< T, U >, std::is_constructible< E, G > >, bool > = true>

sen::Result< T, E >::Result ( Result< U, G > && other )

inline

Do a conversion construction from a compatible Result.

Member Function Documentation

operator==()

template<typename T, typename E>

bool sen::Result< T, E >::operator== ( const Result< T, E > & other ) const

inline

operator!=()

template<typename T, typename E>

bool sen::Result< T, E >::operator!= ( const Result< T, E > & other ) const

inline

isOk()

template<typename T, typename E>

bool sen::Result< T, E >::isOk ( ) const

inlinenodiscardnoexcept

Used to determine if the result is not an error.

Returns

true - object holds a valid data of type T false - object does not hold valid data of type T

isError()

template<typename T, typename E>

bool sen::Result< T, E >::isError ( ) const

inlinenodiscardnoexcept

Used to determine if the result is an error.

Returns

true - object holds an error of type E false - object does not hold an error of type E

operator bool()

template<typename T, typename E>

sen::Result< T, E >::operator bool ( ) const

inlineexplicitnoexcept

Used to determine if the result is not an error.

Returns

true - object holds a valid data of type T false - object does not hold valid data of type T

getValueOr()

template<typename T, typename E>

template<typename U>

const impl::NonVoidT< U > & sen::Result< T, E >::getValueOr ( const U & defaultVal ) const

inlinenodiscardnoexcept

Used to determine the return value. If the result indicates an error this method will return defaultValue.

Parameters

defaultVal

The value to be used in case of holding an error.

Returns

defaultVal if this object holds an error, the stored success value otherwise.

getValue() [1/2]

template<typename T, typename E>

template<typename U = T>

const impl::NonVoidT< U > & sen::Result< T, E >::getValue ( ) const &

inlinenodiscard

Used to determine the success value, given that there is no error.

Warning

if this object holds an error, calling this function will cause program to terminate.

Precondition

isOk() || !isError()

Returns

the success value stored in this object.

getValue() [2/2]

template<typename T, typename E>

template<typename U = T>

impl::NonVoidT< U > && sen::Result< T, E >::getValue ( ) &&

inlinenodiscard

Used to move out the success value, given that there is no error.

Warning

if this object holds an error, calling this function will cause program to terminate.

Precondition

isOk() || !isError()

Returns

the success value stored in this object.

getError()

template<typename T, typename E>

const E & sen::Result< T, E >::getError ( ) const

inlinenodiscard

Used to determine the error value, given that there is an error.

Warning

if this object does not hold an error, calling this function will cause program to terminate.

Precondition

isError() || !isOk()

Returns

the error value stored in this object.

expect()

template<typename T, typename E>

template<typename U = T>

const impl::NonVoidT< U > & sen::Result< T, E >::expect ( std::string_view errorMsg = {} ) const

inlinenodiscardnoexcept

Extracts the value of the correct result, or terminates the program with a given error message.

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The documentation for this class was generated from the following file:

• result.h