Mdt::Expected< T > Class Template Reference

Contains a value or a error. More...

#include <Expected.h>

Collaboration diagram for Mdt::Expected< T >:

Public Member Functions
	Expected ()
	Construct a empty expected. More...
	Expected (const T &v)
	Construct a expected with a value.
	Expected (T &&v)
	Construct a expected with a value.
	Expected (const Mdt::Error &e)
	Construct a expected with a error.
	Expected (Mdt::Error &&e)
	Construct a expected with a error.
	Expected (const Expected &other)
	Construct a copy of other.
	Expected (Expected &&other)
	Construct by moving other.
	~Expected ()
	Destructor.
Expected &	operator= (const T &v)
	Assign a value.
Expected &	operator= (T &&v)
	Assign a value.
Expected &	operator= (const Mdt::Error &e)
	Assign a error.
Expected &	operator= (Mdt::Error &&e)
	Assign a error.
Expected &	operator= (const Expected &other)
	Assign a Expected.
Expected &	operator= (Expected &&other)
	Assign a Expected.
bool	hasError () const
	Return true if a error was set.
Mdt::Error &	error ()
	Access error. More...
const Mdt::Error &	error () const
	Access error (read only) More...
bool	hasValue () const
	Return true if a value was set.
T &	value ()
	Access value. More...
const T &	value () const
	Access value (read only) More...
constexpr	operator bool () const noexcept
	Return true if a value was set.
T &	operator* ()&
	Access value. More...
const T &	operator* () const &
	Access value (read only) More...

Detailed Description

template<typename T>
class Mdt::Expected< T >

Contains a value or a error.

Expected provides a basic support of expected value. This is inspired from A. Alexandrescu 's talk "Systematic Error Handling in C++" : http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Andrei-Alexandrescu-Systematic-Error-Handling-in-C

Mdt::Expected is a very limited version of the concept. For more advanced and performant version, you should take a look at the official proposal: https://github.com/viboes/std-make/tree/master/doc/proposal/expected

A function, that reads a value from a storage, could look like:

Mdt::Expected<int> readValue(const QString & filePath);

Later, a computation has to be done on the readen value:

int compute(int value);

Using all together could be:

const auto x = readValue("/path/to/x.csv");
if(!x){
  // Error handling
  return -1;
}
const auto y = compute(*x);

Template Parameters

T	Type of value

Definition at line 64 of file Expected.h.

Constructor & Destructor Documentation

template<typename T>

Mdt::Expected< T >::Expected ( )

inline

Construct a empty expected.

A empty expected contains a null error (see Mdt::Error::isNull()).

Definition at line 73 of file Expected.h.

Member Function Documentation

template<typename T>

Mdt::Error& Mdt::Expected< T >::error ( )

inline

Access error.

Precondition

this must contain a error

Definition at line 246 of file Expected.h.

template<typename T>

const Mdt::Error& Mdt::Expected< T >::error ( ) const

inline

Access error (read only)

Precondition

this must contain a error

Definition at line 256 of file Expected.h.

template<typename T>

T& Mdt::Expected< T >::operator* ( )

inline

Access value.

Precondition

this must contain a value

Definition at line 300 of file Expected.h.

template<typename T>

const T& Mdt::Expected< T >::operator* ( ) const

inline

Access value (read only)

Precondition

this must contain a value

Definition at line 310 of file Expected.h.

template<typename T>

T& Mdt::Expected< T >::value ( )

inline

Access value.

Precondition

this must contain a value

Definition at line 273 of file Expected.h.

template<typename T>

const T& Mdt::Expected< T >::value ( ) const

inline

Access value (read only)

Precondition

this must contain a value

Definition at line 283 of file Expected.h.

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

• libs/Expected/src/Mdt/Expected.h