Struct tokio::sync::MutexGuard
source · pub struct MutexGuard<'a, T: ?Sized> { /* private fields */ }
Expand description
A handle to a held Mutex
. The guard can be held across any .await
point
as it is Send
.
As long as you have this guard, you have exclusive access to the underlying
T
. The guard internally borrows the Mutex
, so the mutex will not be
dropped while a guard exists.
The lock is automatically released whenever the guard is dropped, at which
point lock
will succeed yet again.
Implementations§
source§impl<'a, T: ?Sized> MutexGuard<'a, T>
impl<'a, T: ?Sized> MutexGuard<'a, T>
sourcepub fn map<U, F>(this: Self, f: F) -> MappedMutexGuard<'a, U>
pub fn map<U, F>(this: Self, f: F) -> MappedMutexGuard<'a, U>
Makes a new MappedMutexGuard
for a component of the locked data.
This operation cannot fail as the MutexGuard
passed in already locked the mutex.
This is an associated function that needs to be used as MutexGuard::map(...)
. A method
would interfere with methods of the same name on the contents of the locked data.
§Examples
use tokio::sync::{Mutex, MutexGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let foo = Mutex::new(Foo(1));
{
let mut mapped = MutexGuard::map(foo.lock().await, |f| &mut f.0);
*mapped = 2;
}
assert_eq!(Foo(2), *foo.lock().await);
sourcepub fn try_map<U, F>(this: Self, f: F) -> Result<MappedMutexGuard<'a, U>, Self>
pub fn try_map<U, F>(this: Self, f: F) -> Result<MappedMutexGuard<'a, U>, Self>
Attempts to make a new MappedMutexGuard
for a component of the locked data. The
original guard is returned if the closure returns None
.
This operation cannot fail as the MutexGuard
passed in already locked the mutex.
This is an associated function that needs to be used as MutexGuard::try_map(...)
. A
method would interfere with methods of the same name on the contents of the locked data.
§Examples
use tokio::sync::{Mutex, MutexGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let foo = Mutex::new(Foo(1));
{
let mut mapped = MutexGuard::try_map(foo.lock().await, |f| Some(&mut f.0))
.expect("should not fail");
*mapped = 2;
}
assert_eq!(Foo(2), *foo.lock().await);
sourcepub fn mutex(this: &Self) -> &'a Mutex<T>
pub fn mutex(this: &Self) -> &'a Mutex<T>
Returns a reference to the original Mutex
.
use tokio::sync::{Mutex, MutexGuard};
async fn unlock_and_relock<'l>(guard: MutexGuard<'l, u32>) -> MutexGuard<'l, u32> {
println!("1. contains: {:?}", *guard);
let mutex = MutexGuard::mutex(&guard);
drop(guard);
let guard = mutex.lock().await;
println!("2. contains: {:?}", *guard);
guard
}