Struct VarReadGuard 

pub struct VarReadGuard<'a, T: ?Sized + Send + Sync + 'static> { /* private fields */ }

A read lock guard returned by Var::read or WeakVar::read.

While the guard is alive, it holds a shared lock on the underlying value. When the guard is dropped, the variable is registered as having been read so viewports can track dependencies.

Mapped guards produced by VarReadGuard::map and friends preserve the same behavior: dependency tracking happens when the final mapped guard is dropped.

Implementations

impl<'a, T: ?Sized + Send + Sync + 'static> VarReadGuard<'a, T>

pub fn map<U: ?Sized + Send + Sync + 'static>( this: Self, f: impl FnOnce(&T) -> &U, ) -> VarReadGuard<'a, U>

Maps a read guard to a subfield, like RwLockReadGuard::map.

This is an associated function that needs to be used as VarReadGuard::map(...).

pub fn try_map<U: ?Sized + Send + Sync + 'static>( this: Self, f: impl FnOnce(&T) -> Option<&U>, ) -> Result<VarReadGuard<'a, U>, VarReadGuard<'a, T>>

Fallible map, like RwLockReadGuard::try_map.

This is an associated function that needs to be used as VarReadGuard::try_map(...).

pub fn try_map_or_err<U: ?Sized + Send + Sync + 'static, E>( this: Self, f: impl FnOnce(&T) -> Result<&U, E>, ) -> Result<VarReadGuard<'a, U>, (VarReadGuard<'a, T>, E)>

Fallible map, like RwLockReadGuard::try_map, but returns the error produced by the mapping function.

This is an associated function that needs to be used as VarReadGuard::try_map_or_err(...).

Trait Implementations

impl<'a, T: ?Sized + Send + Sync + 'static> Deref for VarReadGuard<'a, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<'a, T: ?Sized + Send + Sync + 'static> Drop for VarReadGuard<'a, T>

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.