Struct core::cell::Ref
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[src]
pub struct Ref<'b, T: ?Sized + 'b> {
_value: &'b T,
_borrow: BorrowRef<'b>,
}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.
Fields
_value | |
_borrow |
Methods
impl<'b, T: ?Sized> Ref<'b, T>
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.
fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U> where F: FnOnce(&T) -> &U
Make 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.
Example
#![feature(cell_extras)] fn main() { 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) }#![feature(cell_extras)] 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)
fn filter_map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Option<Ref<'b, U>> where F: FnOnce(&T) -> Option<&U>
Make a new Ref for an optional component of the borrowed data, e.g. an
enum variant.
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.
Example
#![feature(cell_extras)] fn main() { use std::cell::{RefCell, Ref}; let c = RefCell::new(Ok(5)); let b1: Ref<Result<u32, ()>> = c.borrow(); let b2: Ref<u32> = Ref::filter_map(b1, |o| o.as_ref().ok()).unwrap(); assert_eq!(*b2, 5) }use std::cell::{RefCell, Ref}; let c = RefCell::new(Ok(5)); let b1: Ref<Result<u32, ()>> = c.borrow(); let b2: Ref<u32> = Ref::filter_map(b1, |o| o.as_ref().ok()).unwrap(); assert_eq!(*b2, 5)