Struct Once

pub struct Once<T>(/* private fields */);

Special user-data wrapper intended for objects that can only be used once. Only implements MapOwned.

Trait Implementations

impl<T> Clone for Once<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> MapOwned for Once<T>

where T: NativeClass + Send,

fn map_owned<F, U>(&self, op: F) -> Result<U, Self::Err>

where F: FnOnce(Self::Target) -> U,

Maps a T to U. Called for methods that take self. This method may fail with an error if it is called more than once on the same object.

Implementations of this method must not panic. Failures should be indicated by returning Err.

type Err = ValueTaken

impl<T> UserData for Once<T>

where T: NativeClass + Send,

type Target = T

fn new(val: Self::Target) -> Self

Creates a new owned wrapper from a NativeClass instance.

fn into_user_data(self) -> *const c_void

Takes a native instance and returns an opaque pointer that can be used to recover it.

unsafe fn consume_user_data_unchecked(ptr: *const c_void) -> Self

Takes an opaque pointer produced by into_user_data and “consumes” it to produce the original instance, keeping the reference count.

unsafe fn clone_from_user_data_unchecked(ptr: *const c_void) -> Self

Takes an opaque pointer produced by into_user_data and “clones” it to produce the original instance, increasing the reference count.