Struct MaybeEmpty 

pub struct MaybeEmpty<T>(/* private fields */)
where
    T: IsEmpty;

A wrapper type to represent an instance of a type T that may be in a well-known “empty” state where its usual guarantees aren’t upheld.

This is similar to MaybeUninit in that it ensures that the underlying structure isn’t accessed until we’re confident it’s valid, but it’s different in that the memory is actually initialized. It’s just initialized to a known pattern that indicates an empty or null value. The specific pattern differs from type to type; individual types implement the IsEmpty trait to determine when the structure is valid.

This is also similar to Option. The main difference is that this is usable for complex structs defined in C++, while Option is only usable for pointers and Rust structs.

Implementations

impl<T> MaybeEmpty<T>

where T: IsEmpty,

pub fn is_empty(&self) -> bool

Returns whether this struct is “empty” according to its own internal logic.

pub fn as_non_null(&self) -> NonNull<T>

Gets a pointer to the contained value. Reading from this pointer is unsafe but well-defined, since the underlying memory will either be a valid T or match the well-known empty pattern.

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

If this isn’t empty, returns it. Otherwise, returns None.

pub fn as_option_mut(&mut self) -> Option<&mut T>

If this isn’t empty, returns it. Otherwise, returns None.

Trait Implementations

impl<T> Debug for MaybeEmpty<T>

where T: IsEmpty + Debug,

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

Formats the value using the given formatter.