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litert:: Expected

#include <litert_expected.h>

A utility for generic return values that may represent a failure.

Summary

Expected stores and owns the lifetime of either an Unexpected object or a value of type T . T can be any primitive or non-primitive type.

No dynamic allocations occur during initialization, so the underlying T is only movable (as opposed to being releasable). Arguments should be constructed in-place when initializing the Expected object if possible.

Unexpected && and T&& can be implicitly cast to an Expected . For example:

 Expected 
   
 Bar 
 () 
  
 { 
  
 bool 
  
 success 
  
 = 
  
 ... 
  
 if 
  
 (!success) 
  
 { 
  
 return 
  
 Unexpected( 
 Status 
 : 
 : 
 kErrorUnknown 
 , 
  
 "Bad Baz" 
 ); 
  
 } 
  
 return 
  
 Foo 
 (); 
 }

Constructors and Destructors

 Expected 
(std::initializer_list< U > il)

Constructs T from an initializer list in-place.

 Expected 
(Args &&... args)

Constructs T from forwarded arguments in-place.

 Expected 
(reference t)

Allows for implicit conversion from a convertible T value in-place.

 Expected 
(const U & t)

Copy-constructs from a constant reference.

 Expected 
( value_type 
&& t)

 Expected 
(const Unexpected 
& err)

Constructs from an

 Unexpected

object in-place.

 Expected 
( Unexpected 
&& err)

 Expected 
(const class Error 
& e)

 Expected 
( Expected 
&& other)

 Expected 
(const Expected 
& other)

 ~Expected 
()

Public types

 StorageType

using

std::conditional_t< std::is_reference_v< T >, std::reference_wrapper< std::remove_reference_t< T >>, T >

 const_pointer

using

const value_type 
*

 const_reference

using

const value_type 
&

 pointer

using

std::remove_reference_t< T > *

 reference

using

std::remove_reference_t< T > &

 value_type

using

std::decay_t< T >

The following type definitions are in snake_case to match standard member types.

Public attributes

 unexpected_

 Unexpected

 value_

StorageType

Public functions

 Error 
() const &

const class Error 
&

Observer for

 Unexpected

 Error 
()&

class Error 
&

 Error 
() const &&=delete

const class Error 
&&

Deleted: an

 Expected

should always be checked before accessing its error.

 Error 
()&&=delete

class Error 
&&

Deleted: an

 Expected

should always be checked before accessing its error.

 HasValue 
() const

bool

Checks if this

 Expected

contains a T value.

 Value 
() const &

const_reference

Observers for the T value.

 Value 
()&

reference

 Value 
() const &&=delete

reference &

Deleted: an

 Expected

should always be checked before accessing its value.

 Value 
()&&=delete

reference &

Deleted: an

 Expected

should always be checked before accessing its value.

 operator bool 
() const

Converts to bool for HasValue .

 operator* 
() const &

const_reference

 operator* 
()&

reference

 operator* 
() const &&=delete

reference &

Deleted: an

 Expected

should always be checked before accessing its value.

 operator* 
()&&=delete

reference &

Deleted: an

 Expected

should always be checked before accessing its value.

 operator-> 
() const &

const_pointer

 operator-> 
()&

pointer

 operator-> 
() const &&=delete

const_pointer

Deleted: an

 Expected

should always be checked before accessing its value.

 operator-> 
()&&=delete

pointer

Deleted: an

 Expected

should always be checked before accessing its value.

 operator= 
( Expected 
&& other)

 Expected 
&

 operator= 
(const Expected 
& other)

 Expected 
&

Public types

StorageType

std::conditional_t< std::is_reference_v< T >, std::reference_wrapper< std::remove_reference_t< T >>, T > StorageType

const_pointer

 const 
  
  value_type 
 
  
 * 
  
 const_pointer

const_reference

 const 
  
  value_type 
 
 & 
 const_reference

pointer

std::remove_reference_t< T > * pointer

reference

std::remove_reference_t< T > & reference

value_type

 std 
 :: 
 decay_t 
<  
 T 
 > 
 value_type

The following type definitions are in snake_case to match standard member types.

Public attributes

unexpected_

 Unexpected 
unexpected_

value_

StorageType value_

Public functions

Error

 const 
  
 class 
  
  Error 
 
 & 
 Error 
 () 
  
 const 
  
&

Observer for Unexpected .

The program exits if it doesn't have one.

Error

 class 
  Error 
 
& Error 
()&

Error

 const 
  
 class 
  
  Error 
 
 && 
 Error 
 () 
  
 const 
  
&& = 
 delete

Deleted: an Expected should always be checked before accessing its error.

Error

 class 
  Error 
 
&& Error 
()&&= delete

Deleted: an Expected should always be checked before accessing its error.

Expected

Expected(
  std::initializer_list< U > il
)

Constructs T from an initializer list in-place.

Expected

Expected(
  Args &&... args
)

Constructs T from forwarded arguments in-place.

Expected

Expected(
  reference t
)

Allows for implicit conversion from a convertible T value in-place.

Expected

  
 Expected 
 ( 
  
 const 
  
 U 
 & 
 t 
 )

Copy-constructs from a constant reference.

This is disabled if T is a constant reference.

Expected

  
 Expected 
 ( 
  
  value_type 
 
 && 
 t 
 )

Expected

  
 Expected 
 ( 
  
 const 
  
  Unexpected 
 
 & 
 err 
 )

Constructs from an Unexpected object in-place.

Allows for implicit conversion from Error .

Expected

Expected( Unexpected 
&& err
)

Expected

  
 Expected 
 ( 
  
 const 
  
 class 
  
  Error 
 
 & 
 e 
 )

Expected

Expected( Expected 
&& other
)

Expected

  
 Expected 
 ( 
  
 const 
  
  Expected 
 
 & 
 other 
 )

HasValue

 bool 
  
 HasValue 
 () 
  
 const

Checks if this Expected contains a T value.

If not, it contains an Unexpected .

Value

 const_reference 
  
 Value 
 () 
  
 const 
  
&

Observers for the T value.

The program exits if it doesn't have one.

Value

reference Value()&

Value

 reference 
 & 
 Value 
 () 
  
 const 
  
&& = 
 delete

Deleted: an Expected should always be checked before accessing its value.

Value

reference & Value()&&=delete

Deleted: an Expected should always be checked before accessing its value.

operator bool

  
 operator 
  
 bool 
 () 
  
 const

Converts to bool for HasValue .

operator*

 const_reference 
  
 operator 
 * 
 () 
  
 const 
  
&

operator*

reference operator*()&

operator*

 reference 
 & 
 operator 
 * 
 () 
  
 const 
  
&& = 
 delete

Deleted: an Expected should always be checked before accessing its value.

operator*

reference & operator*()&&=delete

Deleted: an Expected should always be checked before accessing its value.

operator->

 const_pointer 
  
 operator 
 - 
> () 
  
 const 
  
&

operator->

pointer operator->()&

operator->

 const_pointer 
  
 operator 
 - 
> () 
  
 const 
  
&& = 
 delete

Deleted: an Expected should always be checked before accessing its value.

operator->

pointer operator->()&&=delete

Deleted: an Expected should always be checked before accessing its value.

operator=

 Expected 
& operator=( Expected 
&& other
)

operator=

  Expected 
 
 & 
 operator 
 = 
 ( 
  
 const 
  
  Expected 
 
 & 
 other 
 )

~Expected

~Expected()