ResultRef< T > Class Template Reference

#include <resultbase.h>

Detailed Description

template<typename T>
class maxon::ResultRef< T >

ResultRef<T> wraps a pointer. When the pointer is nullptr, this has to be interpreted as an out-of-memory error condition, otherwise GetValue() returns the pointer as a C++ reference.

ResultRef<T> can be used instead of the more general Result<T&> when only out-of-memory conditions can occur in a function. It will lead to more efficient code.

Sometimes it is necessary to convert a ResultRef<T> to a ResultPtr<T>, for example if the variable to which the result shall be assigned already exists:

BaseArray<Int> array;
Int& ref = array.Append() iferr_return;
Int* ptr = ...;
if (some condition)
{
  ptr = &array.Append() iferr_return;
}

The result of the second call to Append has to be converted from ResultRef<Int> to ResultPtr<Int> so that (in the successful case) #ptr can be set to a pointer to the new array element. For this purpose the address-of operator & is overloaded at ResultRef to do exactly this conversion.

All error handling features of the Maxon API (such as iferr, iferr_return and Result) support ResultRef.

Public Types
using	IsResult = std::true_type
using	ValueType = T &

Public Member Functions
MAXON_IMPLICIT	ResultRef (T *value=nullptr)
MAXON_IMPLICIT	ResultRef (T &value)
MAXON_IMPLICIT	ResultRef (ERROR_FAILED)
void	operator= (T &)=delete
template<typename T2 , typename = typename std::enable_if<(STD_IS_REPLACEMENT(same, const T, const T2) || STD_IS_REPLACEMENT(base_of, T, T2)) && (STD_IS_REPLACEMENT(const, T) >= STD_IS_REPLACEMENT(const, T2))>::type>
MAXON_IMPLICIT	ResultRef (const ResultRef< T2 > &src)
template<typename T2 , typename = typename std::enable_if<(STD_IS_REPLACEMENT(same, const T, const T2) || STD_IS_REPLACEMENT(base_of, T, T2)) && (STD_IS_REPLACEMENT(const, T) >= STD_IS_REPLACEMENT(const, T2))>::type>
MAXON_IMPLICIT	ResultRef (const ResultPtr< T2 > &src)
Bool	operator== (ERROR_OK) const
Bool	operator== (ERROR_FAILED) const
T &	GetValue () const
T &	UncheckedGetValue () const
const T &	GetValueOr (const T &defaultValue) const
T	GetValueOr (T &&defaultValue) const
const T &	GetValueOrDefault () const
T *	GetPointer () const
void	IfErrIgnore (const char *) const
const ResultPtr< T > &	operator& () const

Static Public Attributes
static constexpr Bool	HAS_ERROR

Private Attributes
T *	_value

Member Typedef Documentation

IsResult

using IsResult = std::true_type

ValueType

using ValueType = T&

Constructor & Destructor Documentation

ResultRef() [1/5]

MAXON_IMPLICIT ResultRef

(

T *

value = nullptr

)

ResultRef() [2/5]

MAXON_IMPLICIT ResultRef

(

T &

value

)

ResultRef() [3/5]

MAXON_IMPLICIT ResultRef

(

ERROR_FAILED

)

ResultRef() [4/5]

MAXON_IMPLICIT ResultRef

(

const ResultRef< T2 > &

src

)

ResultRef() [5/5]

MAXON_IMPLICIT ResultRef

(

const ResultPtr< T2 > &

src

)

Member Function Documentation

operator=()

void operator= ( T &  )

delete

operator==() [1/2]

Bool operator==

(

ERROR_OK

)

const

==(ERROR_OK)

==(ERROR_OK)

operator==() [2/2]

Bool operator==

(

ERROR_FAILED

)

const

==(ERROR_FAILED)

==(ERROR_FAILED)

GetValue()

T& GetValue

(

)

const

Returns the result value. This function must not be called when there is no value because an out-of-memory error occurred.

Returns

Result value.

UncheckedGetValue()

T& UncheckedGetValue

(

)

const

Returns the result value. The result of this function must not be used when there is no value (then it's an invalid C++ reference).

Returns

Result value.

GetValueOr() [1/2]

const T& GetValueOr

(

const T &

defaultValue

)

const

Returns the contained value, or a default value in case of an error.

Parameters

[in]

defaultValue

Default value to be used in case of an error.

GetValueOr() [2/2]

T GetValueOr

(

T &&

defaultValue

)

const

Returns the contained value, or a default value in case of an error.

Parameters

[in]

defaultValue

Default value to be used in case of an error.

Returns

Result value (or default in case of an error).

GetValueOrDefault()

const T& GetValueOrDefault

(

)

const

Returns the contained value, or a default value in case of an error.

Returns

Result value (or default in case of an error).

GetPointer()

T* GetPointer

(

)

const

Returns the result pointer.

Returns

Result pointer.

IfErrIgnore()

void IfErrIgnore

(

const char *

)

const

Allows to skip a returned error and to continue execution.

operator&()

const ResultPtr<T>& operator&

(

)

const

Converts from a ResultRef<T> to a ResultPtr<T>.

Note

Usually it is a really bad idea to overload the address-of operator. But in this case it can't do any harm because ResultRef isn't used in contexts where the normal address-of operator is used. And if & was applied to a ResultRef with the expectation of returning a pointer, the compiler would complain because ResultPtr doesn't mimic pointers at all.

Returns

This ResultRef, cast to a ResultPtr.

Member Data Documentation

HAS_ERROR

constexpr Bool HAS_ERROR

staticconstexpr

_value

T* _value

private