Struct alloc::rc::Rc1.0.0 [] [src]

pub struct Rc<T: ?Sized> { /* fields omitted */ }

A single-threaded reference-counting pointer. 'Rc' stands for 'Reference Counted'.

See the module-level documentation for more details.

The inherent methods of Rc are all associated functions, which means that you have to call them as e.g. Rc::get_mut(&mut value) instead of value.get_mut(). This avoids conflicts with methods of the inner type T.

Methods

impl<T> Rc<T>
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Constructs a new Rc<T>.

Examples

use std::rc::Rc;

let five = Rc::new(5);

1.4.0
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Returns the contained value, if the Rc has exactly one strong reference.

Otherwise, an Err is returned with the same Rc that was passed in.

This will succeed even if there are outstanding weak references.

Examples

use std::rc::Rc;

let x = Rc::new(3);
assert_eq!(Rc::try_unwrap(x), Ok(3));

let x = Rc::new(4);
let _y = Rc::clone(&x);
assert_eq!(*Rc::try_unwrap(x).unwrap_err(), 4);

impl<T: ?Sized> Rc<T>
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1.17.0
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Consumes the Rc, returning the wrapped pointer.

To avoid a memory leak the pointer must be converted back to an Rc using Rc::from_raw.

Examples

use std::rc::Rc;

let x = Rc::new(10);
let x_ptr = Rc::into_raw(x);
assert_eq!(unsafe { *x_ptr }, 10);

1.17.0
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Constructs an Rc from a raw pointer.

The raw pointer must have been previously returned by a call to a Rc::into_raw.

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

Examples

use std::rc::Rc;

let x = Rc::new(10);
let x_ptr = Rc::into_raw(x);

unsafe {
    // Convert back to an `Rc` to prevent leak.
    let x = Rc::from_raw(x_ptr);
    assert_eq!(*x, 10);

    // Further calls to `Rc::from_raw(x_ptr)` would be memory unsafe.
}

// The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!

1.4.0
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Creates a new Weak pointer to this value.

Examples

use std::rc::Rc;

let five = Rc::new(5);

let weak_five = Rc::downgrade(&five);

1.15.0
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Gets the number of Weak pointers to this value.

Examples

use std::rc::Rc;

let five = Rc::new(5);
let _weak_five = Rc::downgrade(&five);

assert_eq!(1, Rc::weak_count(&five));

1.15.0
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Gets the number of strong (Rc) pointers to this value.

Examples

use std::rc::Rc;

let five = Rc::new(5);
let _also_five = Rc::clone(&five);

assert_eq!(2, Rc::strong_count(&five));

1.4.0
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Returns a mutable reference to the inner value, if there are no other Rc or Weak pointers to the same value.

Returns None otherwise, because it is not safe to mutate a shared value.

See also make_mut, which will clone the inner value when it's shared.

Examples

use std::rc::Rc;

let mut x = Rc::new(3);
*Rc::get_mut(&mut x).unwrap() = 4;
assert_eq!(*x, 4);

let _y = Rc::clone(&x);
assert!(Rc::get_mut(&mut x).is_none());

1.17.0
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Returns true if the two Rcs point to the same value (not just values that compare as equal).

Examples

use std::rc::Rc;

let five = Rc::new(5);
let same_five = Rc::clone(&five);
let other_five = Rc::new(5);

assert!(Rc::ptr_eq(&five, &same_five));
assert!(!Rc::ptr_eq(&five, &other_five));

impl<T: Clone> Rc<T>
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1.4.0
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Makes a mutable reference into the given Rc.

If there are other Rc or Weak pointers to the same value, then make_mut will invoke clone on the inner value to ensure unique ownership. This is also referred to as clone-on-write.

See also get_mut, which will fail rather than cloning.

Examples

use std::rc::Rc;

let mut data = Rc::new(5);

*Rc::make_mut(&mut data) += 1;        // Won't clone anything
let mut other_data = Rc::clone(&data);    // Won't clone inner data
*Rc::make_mut(&mut data) += 1;        // Clones inner data
*Rc::make_mut(&mut data) += 1;        // Won't clone anything
*Rc::make_mut(&mut other_data) *= 2;  // Won't clone anything

// Now `data` and `other_data` point to different values.
assert_eq!(*data, 8);
assert_eq!(*other_data, 12);

impl Rc<Any>
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🔬 This is a nightly-only experimental API. (rc_downcast #44608)

Attempt to downcast the Rc<Any> to a concrete type.

Examples

#![feature(rc_downcast)]
use std::any::Any;
use std::rc::Rc;

fn print_if_string(value: Rc<Any>) {
    if let Ok(string) = value.downcast::<String>() {
        println!("String ({}): {}", string.len(), string);
    }
}

fn main() {
    let my_string = "Hello World".to_string();
    print_if_string(Rc::new(my_string));
    print_if_string(Rc::new(0i8));
}

Trait Implementations

impl<T: ?Sized> !Send for Rc<T>
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impl<T: ?Sized> !Sync for Rc<T>
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impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Rc<U>> for Rc<T>
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impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Rc<U>> for Rc<T>
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impl<T: ?Sized> Deref for Rc<T>
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The resulting type after dereferencing.

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Dereferences the value.

impl<T: ?Sized> Drop for Rc<T>
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Drops the Rc.

This will decrement the strong reference count. If the strong reference count reaches zero then the only other references (if any) are Weak, so we drop the inner value.

Examples

use std::rc::Rc;

struct Foo;

impl Drop for Foo {
    fn drop(&mut self) {
        println!("dropped!");
    }
}

let foo  = Rc::new(Foo);
let foo2 = Rc::clone(&foo);

drop(foo);    // Doesn't print anything
drop(foo2);   // Prints "dropped!"

impl<T: ?Sized> Clone for Rc<T>
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Makes a clone of the Rc pointer.

This creates another pointer to the same inner value, increasing the strong reference count.

Examples

use std::rc::Rc;

let five = Rc::new(5);

Rc::clone(&five);

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Performs copy-assignment from source. Read more

impl<T: Default> Default for Rc<T>
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Creates a new Rc<T>, with the Default value for T.

Examples

use std::rc::Rc;

let x: Rc<i32> = Default::default();
assert_eq!(*x, 0);

impl<T: ?Sized + PartialEq> PartialEq for Rc<T>
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Equality for two Rcs.

Two Rcs are equal if their inner values are equal.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five == Rc::new(5));

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Inequality for two Rcs.

Two Rcs are unequal if their inner values are unequal.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five != Rc::new(6));

impl<T: ?Sized + Eq> Eq for Rc<T>
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impl<T: ?Sized + PartialOrd> PartialOrd for Rc<T>
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Partial comparison for two Rcs.

The two are compared by calling partial_cmp() on their inner values.

Examples

use std::rc::Rc;
use std::cmp::Ordering;

let five = Rc::new(5);

assert_eq!(Some(Ordering::Less), five.partial_cmp(&Rc::new(6)));

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Less-than comparison for two Rcs.

The two are compared by calling < on their inner values.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five < Rc::new(6));

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'Less than or equal to' comparison for two Rcs.

The two are compared by calling <= on their inner values.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five <= Rc::new(5));

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Greater-than comparison for two Rcs.

The two are compared by calling > on their inner values.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five > Rc::new(4));

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'Greater than or equal to' comparison for two Rcs.

The two are compared by calling >= on their inner values.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five >= Rc::new(5));

impl<T: ?Sized + Ord> Ord for Rc<T>
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Comparison for two Rcs.

The two are compared by calling cmp() on their inner values.

Examples

use std::rc::Rc;
use std::cmp::Ordering;

let five = Rc::new(5);

assert_eq!(Ordering::Less, five.cmp(&Rc::new(6)));

1.21.0
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Compares and returns the maximum of two values. Read more

1.21.0
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Compares and returns the minimum of two values. Read more

impl<T: ?Sized + Hash> Hash for Rc<T>
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Feeds this value into the given [Hasher]. Read more

1.3.0
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Feeds a slice of this type into the given [Hasher]. Read more

impl<T: ?Sized + Display> Display for Rc<T>
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Formats the value using the given formatter. Read more

impl<T: ?Sized + Debug> Debug for Rc<T>
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Formats the value using the given formatter.

impl<T: ?Sized> Pointer for Rc<T>
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Formats the value using the given formatter.

impl<T> From<T> for Rc<T>
1.6.0
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Performs the conversion.

impl<'a, T: Clone> From<&'a [T]> for Rc<[T]>
1.21.0
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Performs the conversion.

impl<'a> From<&'a str> for Rc<str>
1.21.0
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Performs the conversion.

impl From<String> for Rc<str>
1.21.0
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Performs the conversion.

impl<T: ?Sized> From<Box<T>> for Rc<T>
1.21.0
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Performs the conversion.

impl<T> From<Vec<T>> for Rc<[T]>
1.21.0
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Performs the conversion.

impl<T: ?Sized> Borrow<T> for Rc<T>
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Immutably borrows from an owned value. Read more

impl<T: ?Sized> AsRef<T> for Rc<T>
1.5.0
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Performs the conversion.