#include <resultbase.h>

Inheritance diagram for Result< RESULT_TYPE >:

Detailed Description

template<typename RESULT_TYPE>
class maxon::Result< RESULT_TYPE >

The Result class wraps a result value and may also hold an error value. It has to be used for functions or methods which have to indicate that an error happened during their execution so that no normal result value could be computed:

Result<Int> Func()
{
  if (everything ok)
    return 123;
  else
    return IllegalStateError(MAXON_SOURCE_LOCATION, "Illegal state in Func."_s);
}

Functions which don't return a value on success use Result<void> as result type and return OK; as return statement for the successful case. Those functions can also use a ResultMem value in the return statement, this will set an OutOfMemoryError if the ResultMem is false:

Result<void> Func(MyObj*& ptr)
{
  if (some condition)
    return OK;
  ptr = NewObj(MyObj);
  return ResultMem(ptr != nullptr);
}

The result value and error can be obtained via GetValue() and GetError(), respectively. To check if there was an error, you can simply write result == OK or result == FAILED. There are also the macros iferr and iferr_return which help to write error handling code.

Warning: This class is not thread-safe. The Result object just contains a pointer to an Error object and does not increment the reference counter. Instead of storing the result somewhere, use the direct Error class.

In the following example the Result is a member of a class. The Result will keep the pointer to the Error object, but it does not keep it alive.

class Foo
{
private:
  Result<void> _result; // BAD!
public:
  Result<void> GetResult()
  {
    return _result;
  }
}

The alternative is to store the error object. The Error object is reference counted and your object of Foo will keep a reference to it, until the object itself is freed. As long as no error is set (GetResult() == OK) will return true.

class Foo
{
private:
  Error _err; // FINE!
public:
  Result<void> GetResult()
  {
    return _err;
  }
}

Template Parameters

RESULT_TYPE Type of result value.

See also: $ref error_result

Public Types
using	Super = typename ResultSuper< RESULT_TYPE, void >::type

Public Types inherited from ResultBase< T >
using	ValueType = T

Public Member Functions
	Result ()

MAXON_IMPLICIT	Result (ErrorPtr &error)

MAXON_IMPLICIT	Result (ErrorPtr &&error)

MAXON_IMPLICIT	Result (const ErrorPtr &error)

MAXON_IMPLICIT	Result (const ThreadReferencedError &error)

MAXON_IMPLICIT	Result (typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ResultMem, const volatile DummyParamType & >::type value)

template<typename T2 , typename = typename Super::template ConstructibleFrom<typename std::add_const<T2>::type>::type>
MAXON_IMPLICIT	Result (const ResultOk< T2 > &value)

template<typename T2 , typename = typename Super::template ConstructibleFrom<T2>::type>
MAXON_IMPLICIT	Result (ResultOk< T2 > &&value)

MAXON_IMPLICIT	Result (typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ResultOk< RESULT_TYPE >, DummyParamType && >::type value)

template<typename T2 >
MAXON_IMPLICIT	Result (const ResultMemT< T2 > &value, typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type=(DummyParamType *) nullptr)

template<typename T2 , typename = typename Super::template ConstructibleFrom<typename std::add_const<T2>::type>::type>
MAXON_IMPLICIT	Result (const ResultMemT< T2 > &value)

template<typename T2 , typename = typename Super::template ConstructibleFrom<T2>::type>
MAXON_IMPLICIT	Result (ResultMemT< T2 > &&value)

template<typename T2 >
MAXON_IMPLICIT	Result (const ResultRef< T2 > &value, typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type=(DummyParamType *) nullptr)

template<typename T2 , typename = typename Super::template ConstructibleFrom<T2&>::type>
MAXON_IMPLICIT	Result (const ResultRef< T2 > &value)

MAXON_IMPLICIT	Result (typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ERROR_OK, volatile DummyParamType & >::type)

MAXON_IMPLICIT	Result (typename std::conditional< T_IS_ERROR, const DummyParamType &, CopyType >::type value)

MAXON_IMPLICIT	Result (typename std::conditional< T_IS_ERROR, DummyParamType &, MoveType >::type value)

MAXON_IMPLICIT	Result (typename std::conditional< T_IS_ERROR, const DummyParamType &&, DeleteType >::type value)=delete

template<typename T2 , typename = typename std::enable_if<!maxon::HasBaseDetector<typename std::decay<T2>::type::ReferencedType, ErrorInterface>::value, RESULT_TYPE>::type::ReferencedType, typename = typename Super::template ConstructibleFrom<T2>::type>
MAXON_IMPLICIT	Result (T2 &&value)

template<typename T2 >
	Result (const Result< T2 > &src, typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type=(DummyParamType *) nullptr)

template<typename T2 , typename = typename Super::template ConstructibleFrom<typename std::add_const<T2>::type>::type>
MAXON_IMPLICIT	Result (const Result< T2 > &src)

template<typename T2 , typename = typename Super::template ConstructibleFrom<T2>::type>
MAXON_IMPLICIT	Result (Result< T2 > &&src)

template<typename E >
MAXON_IMPLICIT	Result (E &&error, typename std::enable_if<!T_IS_ERROR, typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type >::type=(DummyParamType *) nullptr)

template<typename T2 >
	Result (CopyType value, const Result< T2 > &result)

template<typename T2 >
	Result (MoveType value, const Result< T2 > &result)

template<typename T2 >
	Result (DeleteType value, const Result< T2 > &result)=delete

template<typename E >
	Result (CopyType value, E &&error, typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type=(DummyParamType *) nullptr)

template<typename E >
	Result (MoveType value, E &&error, typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type=(DummyParamType *) nullptr)

template<typename E >
	Result (DeleteType value, E &&error, typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type=(DummyParamType *) nullptr)=delete

	Result (typename std::conditional< STD_IS_REPLACEMENT(same, typename std::decay< RESULT_TYPE >::type, Bool), volatile DummyParamType &&, Bool >::type)=delete

SFINAEHelper< Error, RESULT_TYPE >::type	GetError () const

MAXON_ATTRIBUTE_FORCE_INLINE const ErrorInterface *	GetErrorPointer () const

template<typename E >
std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), E >::type	GetError () const

template<typename E >
std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), Bool >::type	HasError () const

Bool	operator== (ERROR_OK ok) const

Bool	operator== (ERROR_FAILED failed) const

void	operator= (typename std::conditional< STD_IS_REPLACEMENT(reference, RESULT_TYPE), RESULT_TYPE, const DummyParamType & >::type)=delete

Public Member Functions inherited from ResultBase< T >
	ResultBase ()

	ResultBase (CopyType value)

	ResultBase (MoveType value)

MAXON_ATTRIBUTE_FORCE_INLINE const T &	GetValue () const &

MAXON_ATTRIBUTE_FORCE_INLINE const T &	UncheckedGetValue () const &

	MAXON_MEMBER_ACCESSORS (T, GetValue)

	MAXON_MEMBER_ACCESSORS (T, UncheckedGetValue)

MAXON_ATTRIBUTE_FORCE_INLINE const T &	GetValueAndError (ThreadReferencedError &error) const &

MAXON_ATTRIBUTE_FORCE_INLINE T	GetValueAndError (ThreadReferencedError &error) &&

MAXON_ATTRIBUTE_FORCE_INLINE const T &	GetValueAndError (Error &error) const &

MAXON_ATTRIBUTE_FORCE_INLINE T	GetValueAndError (Error &error) &&

MAXON_ATTRIBUTE_FORCE_INLINE const ThreadReferencedError &	GetErrorStorage () const

MAXON_ATTRIBUTE_FORCE_INLINE ThreadReferencedError &	GetErrorStorage ()

Static Public Attributes
static const Bool	T_IS_ERROR

Static Public Attributes inherited from ResultBase< T >
static constexpr Bool	HAS_ERROR

Private Member Functions
void	InitError (const Error &error)

void	InitError (Error &&error)

Additional Inherited Members
Protected Types inherited from ResultBase< T >
using	CopyType = typename ByValueParam< T >::type

using	MoveType = typename std::conditional< STD_IS_REPLACEMENT(reference, CopyType), T &&, DummyParamType & >::type

using	DeleteType = const DummyParamType &&

template<typename T2 >
using	ConstructibleFrom = std::enable_if< STD_IS_REPLACEMENT(constructible, T, T2)>

Protected Attributes inherited from ResultBase< T >
ThreadReferencedError	_error

T	_value

Member Typedef Documentation

◆ Super

using Super = typename ResultSuper<RESULT_TYPE, void>::type

Constructor & Destructor Documentation

◆ Result() [1/30]

Result ( )

Constructs a Result object with a null value and no error.

◆ Result() [2/30]

MAXON_IMPLICIT Result ( ErrorPtr & error )

Constructs a Result object with the given error. The result value will be initialized as a null value. This constructor is needed for return err; statements within an iferr block. The extra constructors are required as workaround for MSVC.

Parameters

[in] error Error object to use for the Result.

◆ Result() [3/30]

MAXON_IMPLICIT Result ( ErrorPtr && error )

◆ Result() [4/30]

MAXON_IMPLICIT Result ( const ErrorPtr & error )

◆ Result() [5/30]

MAXON_IMPLICIT Result ( const ThreadReferencedError & error )

◆ Result() [6/30]

MAXON_IMPLICIT Result ( typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ResultMem, const volatile DummyParamType & >::type value )

Constructs a Result<void> object, indicating an OutOfMemoryError if value is false. This constructor is only available for Result<void> and not for a general Result<T>.

Parameters

[in] value If false, set the error object to an OutOfMemoryError.

◆ Result() [7/30]

MAXON_IMPLICIT Result ( const ResultOk< T2 > & value )

Constructs a Result object without error from a ResultOk object.

Parameters

[in] value The ResultOk from which the value is taken.

◆ Result() [8/30]

MAXON_IMPLICIT Result ( ResultOk< T2 > && value )

Constructs a Result object without error from a ResultOk object.

Parameters

[in] value The ResultOk from which the value is taken.

◆ Result() [9/30]

MAXON_IMPLICIT Result ( typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ResultOk< RESULT_TYPE >, DummyParamType && >::type value )

Constructs a Result object without error from a ResultOk object.

Parameters

[in] value The ResultOk from which the value is taken.

◆ Result() [10/30]

MAXON_IMPLICIT Result	(	const ResultMemT< T2 > &	value,
		typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result<void> object, indicating an OutOfMemoryError if value is nullptr. This constructor is only available for Result<void> and not for a general Result<T>.

Parameters

[in] value If nullptr, set the error object to an OutOfMemoryError.

◆ Result() [11/30]

MAXON_IMPLICIT Result ( const ResultMemT< T2 > & value )

Constructs a Result object with a pointer value from a ResultPtr.

Parameters

[in] value The ResultPtr value to use.

◆ Result() [12/30]

MAXON_IMPLICIT Result ( ResultMemT< T2 > && value )

Constructs a Result object with a pointer value from a ResultPtr.

Parameters

[in] value The ResultPtr value to use.

◆ Result() [13/30]

MAXON_IMPLICIT Result	(	const ResultRef< T2 > &	value,
		typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result<void> object, indicating an OutOfMemoryError if value is nullptr. This constructor is only available for Result<void> and not for a general Result<T>.

Parameters

[in] value If nullptr, set the error object to an OutOfMemoryError.

◆ Result() [14/30]

MAXON_IMPLICIT Result ( const ResultRef< T2 > & value )

Constructs a Result object with a C++ reference value from a ResultRef.

Parameters

[in] value The ResultRef value to use.

◆ Result() [15/30]

MAXON_IMPLICIT Result ( typename std::conditional< STD_IS_REPLACEMENT(void, RESULT_TYPE), ERROR_OK, volatile DummyParamType & >::type )

Constructs a Result<void> object without error. This indicates a successful operation, it is typically used implicitly by a return OK; statement. This constructor is only available for Result<void> and not for a general Result<T>.

◆ Result() [16/30]

MAXON_IMPLICIT Result ( typename std::conditional< T_IS_ERROR, const DummyParamType &, CopyType >::type value )

Constructs a Result object with the given result value and without error.

Parameters

[in] value The result value.

◆ Result() [17/30]

MAXON_IMPLICIT Result ( typename std::conditional< T_IS_ERROR, DummyParamType &, MoveType >::type value )

Constructs a Result object with the given result value and without error.

Parameters

[in] value The result value.

◆ Result() [18/30]

MAXON_IMPLICIT Result ( typename std::conditional< T_IS_ERROR, const DummyParamType &&, DeleteType >::type value )

delete

◆ Result() [19/30]

MAXON_IMPLICIT Result ( T2 && value )

Constructs a Result object with the given result value and without error. This constructor is only available for reference classes.

Parameters

[in] value The result value.

◆ Result() [20/30]

Result	(	const Result< T2 > &	src,
		typename std::enable_if< STD_IS_REPLACEMENT(void, typename SFINAEHelper< RESULT_TYPE, T2 >::type), DummyParamType * >::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result<void> object from an existing Result<T2> object src by using the error of src, if any. This constructor is only available for Result<void> and not for a general Result<T>.

◆ Result() [21/30]

MAXON_IMPLICIT Result ( const Result< T2 > & src )

Constructs a Result object from an existing Result object src by using the value and/or error of src.

◆ Result() [22/30]

MAXON_IMPLICIT Result ( Result< T2 > && src )

Constructs a Result object from an existing Result object src by using the value and/or error of src.

◆ Result() [23/30]

MAXON_IMPLICIT Result	(	E &&	error,
		typename std::enable_if<!T_IS_ERROR, typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type	,
		::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result object with the given error. The result value will be initialized as a null value.

Parameters

[in] error Error object to use for the Result.

◆ Result() [24/30]

Result	(	CopyType	value,
		const Result< T2 > &	result
	)

Constructs a Result object with both a value and an error taken from a Result.

Parameters

[in]	value	Result value.
[in]	result	Result object (from which the error is copied).

◆ Result() [25/30]

Result	(	MoveType	value,
		const Result< T2 > &	result
	)

Constructs a Result object with both a value and an error taken from a Result.

Parameters

[in]	value	Result value.
[in]	result	Result object (from which the error is copied).

◆ Result() [26/30]

Result	(	DeleteType	value,
		const Result< T2 > &	result
	)

delete

◆ Result() [27/30]

Result	(	CopyType	value,
		E &&	error,
		typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result object with both a result value and an error.

Parameters

[in]	value	Result value.
[in]	error	Error object.

◆ Result() [28/30]

Result	(	MoveType	value,
		E &&	error,
		typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type	= `(DummyParamType*) nullptr`
	)

Constructs a Result object with both a result value and an error.

Parameters

[in]	value	Result value.
[in]	error	Error object.

◆ Result() [29/30]

Result	(	DeleteType	value,
		E &&	error,
		typename std::enable_if< std::remove_reference< E >::type::DirectlyReferencedType::HasBaseDetector::template Check< ErrorInterface >::value &&MAXON_IS_COW_KIND(std::remove_reference< E >::type::Handler::KIND), DummyParamType * >::type	= `(DummyParamType *) nullptr`
	)

delete

◆ Result() [30/30]

Result ( typename std::conditional< STD_IS_REPLACEMENT(same, typename std::decay< RESULT_TYPE >::type, Bool), volatile DummyParamType &&, Bool >::type )

explicitdelete

Member Function Documentation

◆ GetError() [1/2]

SFINAEHelper<Error, RESULT_TYPE>::type GetError ( void ) const

Returns the error object. If there is no error, this will be a null reference.

Returns: Error object, may be a null reference.

◆ GetErrorPointer()

MAXON_ATTRIBUTE_FORCE_INLINE const ErrorInterface* GetErrorPointer ( ) const

Returns the error object pointer. If there is no error, this will be nullptr.

Returns: Error object pointer, may be nullptr.

◆ GetError() [2/2]

std::enable_if<std::remove_reference<E>::type::DirectlyReferencedType::HasBaseDetector::template Check<ErrorInterface>::value && MAXON_IS_COW_KIND(std::remove_reference<E>::type::Handler::KIND), E >::type GetError ( void ) const

Returns the error object if it is of type E. If there is no error or the error is not an instance of E, a null reference is returned. This function can be used for handling of specific errors as in the following example:

Result<void> result = MyFunc();
if (IllegalArgumentError e = result.GetError<IllegalArgumentError>())
{
  // handle IllegalArgumentError
}
else
{
  // all other errors (if any) are returned to the caller
  result iferr_return;
}

If you don't need the E reference, you can use the HasError() function.

Template Parameters

E	The error reference class to check for.

Returns: Error object of type E, may be a null reference.

◆ HasError()

std::enable_if<std::remove_reference<E>::type::DirectlyReferencedType::HasBaseDetector::template Check<ErrorInterface>::value && MAXON_IS_COW_KIND(std::remove_reference<E>::type::Handler::KIND), Bool >::type HasError ( ) const

Checks if the error object is of type E.

Template Parameters

E	The error reference class to check for.

Returns: True if this Result holds an Error object of type E, false otherwise.

◆ operator==() [1/2]

Bool operator== ( ERROR_OK ok ) const

Checks if this @CLASS indicates a successful operation. Use this operator as in result == OK. To check for a failed operation, you have to use result == FAILED (!= is not supported).

Parameters

[in] ok Use the global constant OK.

Returns: True if this @CLASS has no error.

◆ operator==() [2/2]

Bool operator== ( ERROR_FAILED failed ) const

Checks if this @CLASS indicates a failed operation. Use this operator as in result == FAILED. To check for a successful operation, you have to use result == OK (!= is not supported).

Parameters

[in] failed Use the global constant FAILED.

Returns: True if this @CLASS has an error.

◆ operator=()

void operator= ( typename std::conditional< STD_IS_REPLACEMENT(reference, RESULT_TYPE), RESULT_TYPE, const DummyParamType & >::type )

delete

◆ InitError() [1/2]

void InitError ( const Error & error )

private

◆ InitError() [2/2]

void InitError ( Error && error )

private

Member Data Documentation

◆ T_IS_ERROR

const Bool T_IS_ERROR

static

Detailed Description

template<typename RESULT_TYPE> class maxon::Result< RESULT_TYPE >

Public Types

Public Member Functions

Static Public Attributes

Private Member Functions

Additional Inherited Members

Member Typedef Documentation

◆ Super

Constructor & Destructor Documentation

◆ Result() [1/30]

◆ Result() [2/30]

◆ Result() [3/30]

◆ Result() [4/30]

◆ Result() [5/30]

◆ Result() [6/30]

◆ Result() [7/30]

◆ Result() [8/30]

◆ Result() [9/30]

◆ Result() [10/30]

◆ Result() [11/30]

◆ Result() [12/30]

◆ Result() [13/30]

◆ Result() [14/30]

◆ Result() [15/30]

◆ Result() [16/30]

◆ Result() [17/30]

◆ Result() [18/30]

◆ Result() [19/30]

◆ Result() [20/30]

◆ Result() [21/30]

◆ Result() [22/30]

◆ Result() [23/30]

◆ Result() [24/30]

◆ Result() [25/30]

◆ Result() [26/30]

◆ Result() [27/30]

◆ Result() [28/30]

◆ Result() [29/30]

◆ Result() [30/30]

Member Function Documentation

◆ GetError() [1/2]

◆ GetErrorPointer()

◆ GetError() [2/2]

◆ HasError()

◆ operator==() [1/2]

◆ operator==() [2/2]

◆ operator=()

◆ InitError() [1/2]

◆ InitError() [2/2]

Member Data Documentation

◆ T_IS_ERROR

template<typename RESULT_TYPE>
class maxon::Result< RESULT_TYPE >