Struct MutexGuard 

pub struct MutexGuard<'a, T: ?Sized> { /* private fields */ }

A borrowed proof of exclusive access to a Mutex.

Mutex::lock and Mutex::try_lock create this guard. It dereferences to the protected value and releases the lock when dropped.

Implementations

impl<'a, T: ?Sized> MutexGuard<'a, T>

pub fn map<U, F>(orig: Self, f: F) -> MappedMutexGuard<'a, U>

where F: FnOnce(&mut T) -> &mut U, U: ?Sized,

Projects this guard to a mutable component of the protected value.

The returned guard keeps the same mutex locked. Call this as MutexGuard::map(...) so a method named map on T remains accessible through deref.

Examples

use asyncband::mutex::Mutex;
use asyncband::mutex::MutexGuard;

#[derive(Debug)]
struct User {
    id: u32,
    profile: UserProfile,
}

#[derive(Debug)]
struct UserProfile {
    email: String,
    name: String,
}

let user = User {
    id: 1,
    profile: UserProfile {
        email: "user@example.com".to_owned(),
        name: "Alice".to_owned(),
    },
};

let mutex = Mutex::new(user);
let guard = mutex.lock().await;

// Map to only access the user's profile, allowing fine-grained locking
let profile_guard = MutexGuard::map(guard, |user| &mut user.profile);
assert_eq!(profile_guard.email, "user@example.com");

pub fn filter_map<U, F>( orig: Self, f: F, ) -> Result<MappedMutexGuard<'a, U>, Self>

where F: FnOnce(&mut T) -> Option<&mut U>, U: ?Sized,

Attempts to project this guard to a mutable component of the protected value.

The original guard is returned when f returns None. Call this as MutexGuard::filter_map(...) so a method with the same name on T remains accessible.

Examples

use asyncband::mutex::Mutex;
use asyncband::mutex::MutexGuard;

#[derive(Debug)]
struct Database {
    users: std::collections::HashMap<u32, String>,
    admin_user_id: Option<u32>,
}

let mut db = Database {
    users: std::collections::HashMap::new(),
    admin_user_id: Some(1),
};
db.users.insert(1, "admin@example.com".to_owned());

let mutex = Mutex::new(db);
let guard = mutex.lock().await;

// Try to map to admin user's email if admin exists
let admin_email_guard = MutexGuard::filter_map(guard, |db| {
    if let Some(admin_id) = db.admin_user_id {
        db.users.get_mut(&admin_id)
    } else {
        None
    }
})
.expect("admin user should exist");

assert_eq!(&*admin_email_guard, "admin@example.com");

Trait Implementations

impl<T: ?Sized + Debug> Debug for MutexGuard<'_, T>

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

Formats the value using the given formatter.

impl<T: ?Sized> Deref for MutexGuard<'_, T>

type Target = T

The resulting type after dereferencing.

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

Dereferences the value.

impl<T: ?Sized> DerefMut for MutexGuard<'_, T>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T: ?Sized + Display> Display for MutexGuard<'_, T>

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

Formats the value using the given formatter.

impl<T: ?Sized> Drop for MutexGuard<'_, 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.

impl<T: ?Sized + Send + Sync> Sync for MutexGuard<'_, T>