Struct UnchangedOr

pub struct UnchangedOr<T: ContainerElement = Any> { /* private fields */ }

A typed replacement or an Unchanged marker, stored in one FFI Any cell.

T may be an FFI value type or Any. Use Result<UnchangedOr<T>> to propagate errors. Callbacks can return this wrapper, Unchanged, a replacement value, or a Result containing any of these.

Converting this wrapper to Any preserves the marker. Use Self::value_or or Self::value_or_else when an actual value is needed.

Implementations

impl<T: ContainerElement> UnchangedOr<T>

pub fn unchanged() -> Self

Keep the original value without borrowing or cloning it.

pub fn changed(value: T) -> Self

Supply an owning replacement value.

pub fn is_unchanged(&self) -> bool

Whether this result asks its caller to keep the original value.

pub fn unchanged_or_same_as(&self, original: &T) -> bool

Whether the result is unchanged or has the original shallow identity.

pub fn into_option(self) -> Option<T>

Move out the replacement, returning None when unchanged.

pub fn value_or(self, original: T) -> T

Move the replacement or the supplied original value out of this result.

pub fn value_or_else(self, original: impl FnOnce() -> T) -> T

Materialize the original only if this result is unchanged.

pub fn map<U: ContainerElement>( self, convert: impl FnOnce(T) -> U, ) -> UnchangedOr<U>

Convert only the replacement, preserving an unchanged marker.

pub fn try_map<U: ContainerElement, E>( self, convert: impl FnOnce(T) -> Result<U, E>, ) -> Result<UnchangedOr<U>, E>

Fallibly convert only the replacement, propagating its error unchanged.

pub fn try_cast<U: ContainerElement>(self) -> Result<UnchangedOr<U>>

Check a replacement’s FFI type without cloning it.

An unchanged result is compatible with every replacement type. Erased and narrowing conversions retain the strict type check used by Any::try_as. For a known typed conversion, use map(Into::into).

Trait Implementations

impl<T: ContainerElement> AnyCompatible for UnchangedOr<T>

unsafe fn copy_to_any_view(src: &Self, data: &mut TVMFFIAny)

the value to copy to TVMFFIAny

unsafe fn move_to_any(src: Self, data: &mut TVMFFIAny)

consume the value to move to Any

unsafe fn check_any_strict(data: &TVMFFIAny) -> bool

unsafe fn copy_from_any_view_after_check(data: &TVMFFIAny) -> Self

Copy value from TVMFFIAny after checking caller must ensure that the value is compatible with the type

unsafe fn move_from_any_after_check(data: &mut TVMFFIAny) -> Self

the value to move from TVMFFIAny NOTE: pay very careful attention to avoid memory leak!

unsafe fn try_cast_from_any_view(data: &TVMFFIAny) -> Result<Self, ()>

try to cast the value from AnyView

fn type_str() -> String

the type string of the type

fn type_schema() -> String

The type schema of the type: the JSON object C++ TypeTraits<T>::TypeSchema writes, which the type schemas of functions and fields embed.

unsafe fn is_undefined(field: *const Self) -> bool

Whether field, which holds a value of this type or all-zero bytes, holds all-zero bytes that are no value of this type, as a null object reference, a string of type index None or a zero device type: a field that a creator left undefined for reflection to set, as C++ UnsafeInit leaves a reference undefined (null). Unlike a C++ undefined reference, it is no value; a nullable reference is Option<T>, whose None is a defined value.

fn get_mismatch_type_info(data: &TVMFFIAny) -> String

Get the type key of a type when TryCastFromAnyView fails.

fn to_any(&self) -> Any

Borrow self into an owned Any, increfing object-backed values.

impl<T: ContainerElement> Clone for UnchangedOr<T>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: ContainerElement> TryFrom<Any> for UnchangedOr<T>

type Error = Error

The type returned in the event of a conversion error.

fn try_from(value: Any) -> Result<Self>

Performs the conversion.

impl<'a, T: ContainerElement> TryFrom<AnyView<'a>> for UnchangedOr<T>

type Error = Error

The type returned in the event of a conversion error.

fn try_from(value: AnyView<'a>) -> Result<Self>

Performs the conversion.