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Struct std::cell::Ref

pub struct Ref<'b, T>
where
    T: 'b + ?Sized,{ /* private fields */ }

Wraps a borrowed reference to a value in a RefCell box. A wrapper type for an immutably borrowed value from a RefCell<T>.

See the module-level documentation for more.

Implementations

source 
impl<'b, T> Ref<'b, T>
where
    T: ?Sized,
1.15.0source 
pub fn clone(orig: &Ref<'b, T>) -> Ref<'b, T>

Copies a Ref.

The RefCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::clone(...). A Clone implementation or a method would interfere with the widespread use of r.borrow().clone() to clone the contents of a RefCell.

1.8.0source 
pub fn map<U, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U>
where
    F: FnOnce(&T) -> &U,
    U: ?Sized,

Makes a new Ref for a component of the borrowed data.

The RefCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Examples
use std::cell::{RefCell, Ref};

let c = RefCell::new((5, 'b'));
let b1: Ref<'_, (u32, char)> = c.borrow();
let b2: Ref<'_, u32> = Ref::map(b1, |t| &t.0);
assert_eq!(*b2, 5)
1.63.0source 
pub fn filter_map<U, F>(
    orig: Ref<'b, T>,
    f: F
) -> Result<Ref<'b, U>, Ref<'b, T>>
where
    F: FnOnce(&T) -> Option<&U>,
    U: ?Sized,

Makes a new Ref for an optional component of the borrowed data. The original guard is returned as an Err(..) if the closure returns None.

The RefCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::filter_map(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Examples
use std::cell::{RefCell, Ref};

let c = RefCell::new(vec![1, 2, 3]);
let b1: Ref<'_, Vec<u32>> = c.borrow();
let b2: Result<Ref<'_, u32>, _> = Ref::filter_map(b1, |v| v.get(1));
assert_eq!(*b2.unwrap(), 2);
1.35.0source 
pub fn map_split<U, V, F>(orig: Ref<'b, T>, f: F) -> (Ref<'b, U>, Ref<'b, V>)
where
    F: FnOnce(&T) -> (&U, &V),
    U: ?Sized,
    V: ?Sized,

Splits a Ref into multiple Refs for different components of the borrowed data.

The RefCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map_split(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Examples
use std::cell::{Ref, RefCell};

let cell = RefCell::new([1, 2, 3, 4]);
let borrow = cell.borrow();
let (begin, end) = Ref::map_split(borrow, |slice| slice.split_at(2));
assert_eq!(*begin, [1, 2]);
assert_eq!(*end, [3, 4]);
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pub fn leak(orig: Ref<'b, T>) -> &'b T
🔬This is a nightly-only experimental API. (cell_leak #69099)

Convert into a reference to the underlying data.

The underlying RefCell can never be mutably borrowed from again and will always appear already immutably borrowed. It is not a good idea to leak more than a constant number of references. The RefCell can be immutably borrowed again if only a smaller number of leaks have occurred in total.

This is an associated function that needs to be used as Ref::leak(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Examples
#![feature(cell_leak)]
use std::cell::{RefCell, Ref};
let cell = RefCell::new(0);

let value = Ref::leak(cell.borrow());
assert_eq!(*value, 0);

assert!(cell.try_borrow().is_ok());
assert!(cell.try_borrow_mut().is_err());

Trait Implementations

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impl<T> Debug for Ref<'_, T>
where
    T: Debug + ?Sized,
source 
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
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impl<T> Deref for Ref<'_, T>
where
    T: ?Sized,
 
type Target = T
The resulting type after dereferencing.
source 
fn deref(&self) -> &T
Dereferences the value.
1.20.0source 
impl<T> Display for Ref<'_, T>
where
    T: Display + ?Sized,
source 
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
source 
impl<'b, T, U> CoerceUnsized<Ref<'b, U>> for Ref<'b, T>
where
    T: Unsize<U> + ?Sized,
    U: ?Sized,

Auto Trait Implementations

impl<'b, T> !RefUnwindSafe for Ref<'b, T>
impl<'b, T> !Send for Ref<'b, T>
impl<'b, T> !Sync for Ref<'b, T>
impl<'b, T: ?Sized> Unpin for Ref<'b, T>
impl<'b, T> !UnwindSafe for Ref<'b, T>

Blanket Implementations

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impl<T> Any for T
where
    T: 'static + ?Sized,
source 
fn type_id(&self) -> TypeId
Gets the TypeId of self. Read more
source 
impl<T> Borrow<T> for T
where
    T: ?Sized,
source 
fn borrow(&self) -> &T
Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where
    T: ?Sized,
source 
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
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impl<T> From<T> for T
source 
fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where
    U: From<T>,
source 
fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToString for T
where
    T: Display + ?Sized,
source 
default fn to_string(&self) -> String
Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for T
where
    U: Into<T>,
 
type Error = Infallible
The type returned in the event of a conversion error.
source 
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
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impl<T, U> TryInto<U> for T
where
    U: TryFrom<T>,
 
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
source 
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.

© 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/cell/struct.Ref.html