TValueOrError

Type used to return either a value or an error.

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References

Module	Core
Header	/Engine/Source/Runtime/Core/Public/Math/UnitConversion.inl
Include	#include "Math/UnitConversion.inl"

Syntax

template<typename ValueType, typename ErrorType>
class TValueOrError

Remarks

Type used to return either a value or an error.

These must have a value or an error when newly constructed, but it is possible to have neither because of the functions to steal the value or error. This is critical for callers to consider since it means that HasValue() and HasError() must be checked independently; a return value of false from one does not imply that the other will return true.

The MakeValue and MakeError functions may be used to construct these conveniently.

Constructors

	Name	Description
	TValueOrError ( TValueOrError_ValueProxy< ArgTypes.... )	Construct the value from a proxy from MakeValue.
	TValueOrError ( TValueOrError_ErrorProxy< ArgTypes.... )	Construct the error from a proxy from MakeError.

Functions

	Name	Description
ErrorType	GetError()
const ErrorT...	GetError()
ErrorType &	GetError()	Access the error. Asserts if this does not have an error.
ValueType &	GetValue()	Access the value. Asserts if this does not have a value.
ValueType	GetValue()
const ValueT...	GetValue()
bool	HasError()	Whether the error is set.
bool	HasValue()	Whether the value is set.
bool	IsValid()	Check whether a value is set.
ErrorType	StealError()	Steal the error. Asserts if this does not have an error. This causes the error to be unset.
ValueType	StealValue()	Steal the value. Asserts if this does not have a value. This causes the value to be unset.
ErrorType &#...	TryGetError()	Access the error if it is set.
const ErrorT...	TryGetError()
ValueType &#...	TryGetValue()	Access the value if it is set.
const ValueT...	TryGetValue()