Struct Optional 

pub struct Optional<T: AnyCompatible> { /* private fields */ }

In-place mirror of C++ ffi::Optional<T>: a single 16-byte TVMFFIAny cell (wrapped as Any) whose type_index == kTVMFFINone encodes nullopt.

Layout-compatible with the C++ type (size_of == 16); see the module docs. Reuses Any’s reference-counting Clone/Drop, which are a no-op on the nullopt cell (type_index below kTVMFFIStaticObjectBegin).

Implementations

impl<T: AnyCompatible> Optional<T>

pub fn some(value: T) -> Self

An engaged optional holding value.

pub fn none() -> Self

A disengaged optional (nullopt, a kTVMFFINone cell).

pub fn has_value(&self) -> bool

Whether a value is present.

pub fn is_none(&self) -> bool

Whether the optional is nullopt.

pub fn get(&self) -> Option<T>

Decodes the value in place, cloning it out (ref-counted inc_ref for object payloads). Returns None when nullopt. No FFI call.

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

Takes the value out, consuming self (moves the payload, no inc_ref).

pub fn set(&mut self, value: Option<T>)

Overwrites the value in place, dropping the previous one first (dec-ref’d if it was an object payload).

impl Optional<String>

pub fn as_str(&self) -> Option<&str>

Borrows the engaged string as &str, or None when nullopt.

Reinterprets the in-cell string without cloning: an engaged cell holds a String’s exact 16-byte representation, so &Any can be viewed as &String.

Trait Implementations

impl<T: AnyCompatible> Clone for Optional<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: AnyCompatible + Debug> Debug for Optional<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: AnyCompatible> Default for Optional<T>

fn default() -> Self

nullopt, matching the C++ default constructor.

impl<T: AnyCompatible> From<Option<T>> for Optional<T>

fn from(value: Option<T>) -> Self

Converts to this type from the input type.

impl<T: AnyCompatible> From<Optional<T>> for Option<T>

fn from(value: Optional<T>) -> Self

Converts to this type from the input type.

impl<T: AnyCompatible + PartialEq> PartialEq for Optional<T>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: AnyCompatible + Eq> Eq for Optional<T>