impl<T: ?Sized> OwnedMutexGuard<T>

fn map<U, F>(this: Self, f: F) -> OwnedMappedMutexGuard<T, U>
where
    U: ?Sized,
    F: FnOnce(&mut T) -> &mut U,

Makes a new OwnedMappedMutexGuard for a component of the locked data.

This operation cannot fail as the OwnedMutexGuard passed in already locked the mutex.

This is an associated function that needs to be used as OwnedMutexGuard::map(...). A method would interfere with methods of the same name on the contents of the locked data.

Examples

use tokio::sync::{Mutex, OwnedMutexGuard};
use std::sync::Arc;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);

# #[tokio::main(flavor = "current_thread")]
# async fn main() {
let foo = Arc::new(Mutex::new(Foo(1)));

{
    let mut mapped = OwnedMutexGuard::map(foo.clone().lock_owned().await, |f| &mut f.0);
    *mapped = 2;
}

assert_eq!(Foo(2), *foo.lock().await);
# }

fn try_map<U, F>(this: Self, f: F) -> Result<OwnedMappedMutexGuard<T, U>, Self>
where
    U: ?Sized,
    F: FnOnce(&mut T) -> Option<&mut U>,

Attempts to make a new OwnedMappedMutexGuard for a component of the locked data. The original guard is returned if the closure returns None.

This operation cannot fail as the OwnedMutexGuard passed in already locked the mutex.

This is an associated function that needs to be used as OwnedMutexGuard::try_map(...). A method would interfere with methods of the same name on the contents of the locked data.

Examples

use tokio::sync::{Mutex, OwnedMutexGuard};
use std::sync::Arc;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);

# #[tokio::main(flavor = "current_thread")]
# async fn main() {
let foo = Arc::new(Mutex::new(Foo(1)));

{
    let mut mapped = OwnedMutexGuard::try_map(foo.clone().lock_owned().await, |f| Some(&mut f.0))
        .expect("should not fail");
    *mapped = 2;
}

assert_eq!(Foo(2), *foo.lock().await);
# }

fn mutex(this: &Self) -> &Arc<Mutex<T>>

Returns a reference to the original Arc<Mutex>.

use std::sync::Arc;
use tokio::sync::{Mutex, OwnedMutexGuard};

async fn unlock_and_relock(guard: OwnedMutexGuard<u32>) -> OwnedMutexGuard<u32> {
    println!("1. contains: {:?}", *guard);
    let mutex: Arc<Mutex<u32>> = OwnedMutexGuard::mutex(&guard).clone();
    drop(guard);
    let guard = mutex.lock_owned().await;
    println!("2. contains: {:?}", *guard);
    guard
}
#
# #[tokio::main(flavor = "current_thread")]
# async fn main() {
#     let mutex = Arc::new(Mutex::new(0u32));
#     let guard = mutex.lock_owned().await;
#     unlock_and_relock(guard).await;
# }