pub struct Rc<T> where 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
.
impl<T> Rc<T>
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fn new(value: T) -> Rc<T>
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Constructs a new Rc<T>
.
use std::rc::Rc; let five = Rc::new(5);
fn try_unwrap(this: Rc<T>) -> Result<T, Rc<T>>
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.
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> Rc<T> where
T: ?Sized,
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fn into_raw(this: Rc<T>) -> *const T
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
.
use std::rc::Rc; let x = Rc::new(10); let x_ptr = Rc::into_raw(x); assert_eq!(unsafe { *x_ptr }, 10);
unsafe fn from_raw(ptr: *const T) -> Rc<T>
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.
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!
fn downgrade(this: &Rc<T>) -> Weak<T>
Creates a new Weak
pointer to this value.
use std::rc::Rc; let five = Rc::new(5); let weak_five = Rc::downgrade(&five);
fn weak_count(this: &Rc<T>) -> usize
Gets the number of Weak
pointers to this value.
use std::rc::Rc; let five = Rc::new(5); let _weak_five = Rc::downgrade(&five); assert_eq!(1, Rc::weak_count(&five));
fn strong_count(this: &Rc<T>) -> usize
Gets the number of strong (Rc
) pointers to this value.
use std::rc::Rc; let five = Rc::new(5); let _also_five = Rc::clone(&five); assert_eq!(2, Rc::strong_count(&five));
fn get_mut(this: &mut Rc<T>) -> Option<&mut T>
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.
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());
fn ptr_eq(this: &Rc<T>, other: &Rc<T>) -> bool
Returns true if the two Rc
s point to the same value (not just values that compare as equal).
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> Rc<T> where
T: Clone,
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fn make_mut(this: &mut Rc<T>) -> &mut T
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.
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 + 'static>
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fn downcast<T>(self) -> Result<Rc<T>, Rc<Any + 'static>> where
T: Any,
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Attempt to downcast the Rc<Any>
to a concrete type.
#![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)); }
impl From<String> for Rc<str>
fn from(v: String) -> Rc<str>
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Performs the conversion.
impl<T> From<Vec<T>> for Rc<[T]>
fn from(v: Vec<T>) -> Rc<[T]>
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Performs the conversion.
impl<T> From<T> for Rc<T>
fn from(t: T) -> Rc<T>
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Performs the conversion.
impl<'a, T> From<&'a [T]> for Rc<[T]> where
T: Clone,
fn from(v: &[T]) -> Rc<[T]>
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Performs the conversion.
impl<'a> From<&'a str> for Rc<str>
fn from(v: &str) -> Rc<str>
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Performs the conversion.
impl<T> From<Box<T>> for Rc<T> where
T: ?Sized,
fn from(v: Box<T>) -> Rc<T>
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Performs the conversion.
impl<T, U> CoerceUnsized<Rc<U>> for Rc<T> where
T: Unsize<U> + ?Sized,
U: ?Sized,
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impl<T> PartialOrd<Rc<T>> for Rc<T> where
T: PartialOrd<T> + ?Sized,
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fn partial_cmp(&self, other: &Rc<T>) -> Option<Ordering>
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Partial comparison for two Rc
s.
The two are compared by calling partial_cmp()
on their inner values.
use std::rc::Rc; use std::cmp::Ordering; let five = Rc::new(5); assert_eq!(Some(Ordering::Less), five.partial_cmp(&Rc::new(6)));
fn lt(&self, other: &Rc<T>) -> bool
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Less-than comparison for two Rc
s.
The two are compared by calling <
on their inner values.
use std::rc::Rc; let five = Rc::new(5); assert!(five < Rc::new(6));
fn le(&self, other: &Rc<T>) -> bool
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'Less than or equal to' comparison for two Rc
s.
The two are compared by calling <=
on their inner values.
use std::rc::Rc; let five = Rc::new(5); assert!(five <= Rc::new(5));
fn gt(&self, other: &Rc<T>) -> bool
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Greater-than comparison for two Rc
s.
The two are compared by calling >
on their inner values.
use std::rc::Rc; let five = Rc::new(5); assert!(five > Rc::new(4));
fn ge(&self, other: &Rc<T>) -> bool
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'Greater than or equal to' comparison for two Rc
s.
The two are compared by calling >=
on their inner values.
use std::rc::Rc; let five = Rc::new(5); assert!(five >= Rc::new(5));
impl<T> PartialEq<Rc<T>> for Rc<T> where
T: PartialEq<T> + ?Sized,
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fn eq(&self, other: &Rc<T>) -> bool
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Equality for two Rc
s.
Two Rc
s are equal if their inner values are equal.
use std::rc::Rc; let five = Rc::new(5); assert!(five == Rc::new(5));
fn ne(&self, other: &Rc<T>) -> bool
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Inequality for two Rc
s.
Two Rc
s are unequal if their inner values are unequal.
use std::rc::Rc; let five = Rc::new(5); assert!(five != Rc::new(6));
impl<T> Drop for Rc<T> where
T: ?Sized,
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fn drop(&mut self)
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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.
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> !Send for Rc<T> where
T: ?Sized,
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impl<T> Default for Rc<T> where
T: Default,
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fn default() -> Rc<T>
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Creates a new Rc<T>
, with the Default
value for T
.
use std::rc::Rc; let x: Rc<i32> = Default::default(); assert_eq!(*x, 0);
impl<T> Debug for Rc<T> where
T: Debug + ?Sized,
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
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Formats the value using the given formatter. Read more
impl<T> Borrow<T> for Rc<T> where
T: ?Sized,
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fn borrow(&self) -> &T
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Immutably borrows from an owned value. Read more
impl<T> Hash for Rc<T> where
T: Hash + ?Sized,
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fn hash<H>(&self, state: &mut H) where
H: Hasher,
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Feeds this value into the given [Hasher
]. Read more
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
Feeds a slice of this type into the given [Hasher
]. Read more
impl<T> !Sync for Rc<T> where
T: ?Sized,
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impl<T> AsRef<T> for Rc<T> where
T: ?Sized,
fn as_ref(&self) -> &T
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Performs the conversion.
impl<T> Deref for Rc<T> where
T: ?Sized,
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type Target = T
The resulting type after dereferencing.
fn deref(&self) -> &T
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Dereferences the value.
impl<T> Clone for Rc<T> where
T: ?Sized,
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fn clone(&self) -> 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.
use std::rc::Rc; let five = Rc::new(5); Rc::clone(&five);
fn clone_from(&mut self, source: &Self)
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Performs copy-assignment from source
. Read more
impl<T> Eq for Rc<T> where
T: Eq + ?Sized,
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impl<T> Pointer for Rc<T> where
T: ?Sized,
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
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Formats the value using the given formatter.
impl<T> Display for Rc<T> where
T: Display + ?Sized,
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fn fmt(&self, f: &mut Formatter) -> Result<(), Error>
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Formats the value using the given formatter. Read more
impl<T> Ord for Rc<T> where
T: Ord + ?Sized,
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fn cmp(&self, other: &Rc<T>) -> Ordering
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Comparison for two Rc
s.
The two are compared by calling cmp()
on their inner values.
use std::rc::Rc; use std::cmp::Ordering; let five = Rc::new(5); assert_eq!(Ordering::Less, five.cmp(&Rc::new(6)));
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Rc<T>
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/rc/struct.Rc.html