Struct sharded_slab::pool::OwnedRef
source · pub struct OwnedRef<T, C = DefaultConfig>where
T: Clear + Default,
C: Config,{ /* private fields */ }Expand description
An owned guard that allows shared immutable access to an object in a pool.
While the guard exists, it indicates to the pool that the item the guard references is currently being accessed. If the item is removed from the pool while the guard exists, the removal will be deferred until all guards are dropped.
Unlike Ref, which borrows the pool, an OwnedRef clones the Arc
around the pool. Therefore, it keeps the pool from being dropped until all
such guards have been dropped. This means that an OwnedRef may be held for
an arbitrary lifetime.
Examples
use std::sync::Arc;
let pool: Arc<Pool<String>> = Arc::new(Pool::new());
let key = pool.create_with(|item| item.push_str("hello world")).unwrap();
// Look up the created `Key`, returning an `OwnedRef`.
let value = pool.clone().get_owned(key).unwrap();
// Now, the original `Arc` clone of the pool may be dropped, but the
// returned `OwnedRef` can still access the value.
assert_eq!(value, String::from("hello world"));Unlike Ref, an OwnedRef may be stored in a struct which must live
for the 'static lifetime:
use sharded_slab::pool::OwnedRef;
use std::sync::Arc;
pub struct MyStruct {
pool_ref: OwnedRef<String>,
// ... other fields ...
}
// Suppose this is some arbitrary function which requires a value that
// lives for the 'static lifetime...
fn function_requiring_static<T: 'static>(t: &T) {
// ... do something extremely important and interesting ...
}
let pool: Arc<Pool<String>> = Arc::new(Pool::new());
let key = pool.create_with(|item| item.push_str("hello world")).unwrap();
// Look up the created `Key`, returning an `OwnedRef`.
let pool_ref = pool.clone().get_owned(key).unwrap();
let my_struct = MyStruct {
pool_ref,
// ...
};
// We can use `my_struct` anywhere where it is required to have the
// `'static` lifetime:
function_requiring_static(&my_struct);OwnedRefs may be sent between threads:
use std::{thread, sync::Arc};
let pool: Arc<Pool<String>> = Arc::new(Pool::new());
let key = pool.create_with(|item| item.push_str("hello world")).unwrap();
// Look up the created `Key`, returning an `OwnedRef`.
let value = pool.clone().get_owned(key).unwrap();
thread::spawn(move || {
assert_eq!(value, String::from("hello world"));
// ...
}).join().unwrap();