Struct rquickjs_core::OnceFn

#[repr(transparent)]pub struct OnceFn<F>(_);

The wrapper for once functions

This wrapper is useful for callbacks which can be invoked only once.

Methods from Deref<Target = RefCell<Option<F>>>

pub fn replace(&self, t: T) -> T

Replaces the wrapped value with a new one, returning the old value, without deinitializing either one.

This function corresponds to std::mem::replace.

Panics

Panics if the value is currently borrowed.

Examples

use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace(6);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));

pub fn replace_with<F>(&self, f: F) -> T where
    F: FnOnce(&mut T) -> T, 

Replaces the wrapped value with a new one computed from f, returning the old value, without deinitializing either one.

Panics

Panics if the value is currently borrowed.

Examples

use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace_with(|&mut old| old + 1);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));

pub fn swap(&self, other: &RefCell<T>)

Swaps the wrapped value of self with the wrapped value of other, without deinitializing either one.

This function corresponds to std::mem::swap.

Panics

Panics if the value in either RefCell is currently borrowed.

Examples

use std::cell::RefCell;
let c = RefCell::new(5);
let d = RefCell::new(6);
c.swap(&d);
assert_eq!(c, RefCell::new(6));
assert_eq!(d, RefCell::new(5));

pub fn borrow(&self) -> Ref<'_, T>

Immutably borrows the wrapped value.

The borrow lasts until the returned Ref exits scope. Multiple immutable borrows can be taken out at the same time.

Panics

Panics if the value is currently mutably borrowed. For a non-panicking variant, use try_borrow.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let borrowed_five = c.borrow();
let borrowed_five2 = c.borrow();

An example of panic:

use std::cell::RefCell;

let c = RefCell::new(5);

let m = c.borrow_mut();
let b = c.borrow(); // this causes a panic

pub fn try_borrow(&self) -> Result<Ref<'_, T>, BorrowError>

Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.

The borrow lasts until the returned Ref exits scope. Multiple immutable borrows can be taken out at the same time.

This is the non-panicking variant of borrow.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow_mut();
    assert!(c.try_borrow().is_err());
}

{
    let m = c.borrow();
    assert!(c.try_borrow().is_ok());
}

pub fn borrow_mut(&self) -> RefMut<'_, T>

Mutably borrows the wrapped value.

The borrow lasts until the returned RefMut or all RefMuts derived from it exit scope. The value cannot be borrowed while this borrow is active.

Panics

Panics if the value is currently borrowed. For a non-panicking variant, use try_borrow_mut.

Examples

use std::cell::RefCell;

let c = RefCell::new("hello".to_owned());

*c.borrow_mut() = "bonjour".to_owned();

assert_eq!(&*c.borrow(), "bonjour");

An example of panic:

use std::cell::RefCell;

let c = RefCell::new(5);
let m = c.borrow();

let b = c.borrow_mut(); // this causes a panic

pub fn try_borrow_mut(&self) -> Result<RefMut<'_, T>, BorrowMutError>

Mutably borrows the wrapped value, returning an error if the value is currently borrowed.

The borrow lasts until the returned RefMut or all RefMuts derived from it exit scope. The value cannot be borrowed while this borrow is active.

This is the non-panicking variant of borrow_mut.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow();
    assert!(c.try_borrow_mut().is_err());
}

assert!(c.try_borrow_mut().is_ok());

pub fn as_ptr(&self) -> *mut T

Returns a raw pointer to the underlying data in this cell.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

let ptr = c.as_ptr();

pub unsafe fn try_borrow_unguarded(&self) -> Result<&T, BorrowError>

Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.

Safety

Unlike RefCell::borrow, this method is unsafe because it does not return a Ref, thus leaving the borrow flag untouched. Mutably borrowing the RefCell while the reference returned by this method is alive is undefined behaviour.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);

{
    let m = c.borrow_mut();
    assert!(unsafe { c.try_borrow_unguarded() }.is_err());
}

{
    let m = c.borrow();
    assert!(unsafe { c.try_borrow_unguarded() }.is_ok());
}

pub fn take(&self) -> T

Takes the wrapped value, leaving Default::default() in its place.

Panics

Panics if the value is currently borrowed.

Examples

use std::cell::RefCell;

let c = RefCell::new(5);
let five = c.take();

assert_eq!(five, 5);
assert_eq!(c.into_inner(), 0);

Trait Implementations

impl<'js, F, R> AsFunction<'js, (), R> for OnceFn<F> where
    F: FnOnce() -> R + ParallelSend + 'static,
    R: IntoJs<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A, B, D, E, G, H> AsFunction<'js, (A, B, D, E, G, H), R> for OnceFn<F> where
    F: FnOnce(A, B, D, E, G, H) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>,
    B: FromInput<'js>,
    D: FromInput<'js>,
    E: FromInput<'js>,
    G: FromInput<'js>,
    H: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A, B, D, E, G> AsFunction<'js, (A, B, D, E, G), R> for OnceFn<F> where
    F: FnOnce(A, B, D, E, G) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>,
    B: FromInput<'js>,
    D: FromInput<'js>,
    E: FromInput<'js>,
    G: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A, B, D, E> AsFunction<'js, (A, B, D, E), R> for OnceFn<F> where
    F: FnOnce(A, B, D, E) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>,
    B: FromInput<'js>,
    D: FromInput<'js>,
    E: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A, B, D> AsFunction<'js, (A, B, D), R> for OnceFn<F> where
    F: FnOnce(A, B, D) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>,
    B: FromInput<'js>,
    D: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A, B> AsFunction<'js, (A, B), R> for OnceFn<F> where
    F: FnOnce(A, B) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>,
    B: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<'js, F, R, A> AsFunction<'js, (A,), R> for OnceFn<F> where
    F: FnOnce(A) -> R + ParallelSend + 'static,
    R: IntoJs<'js>,
    A: FromInput<'js>, 

fn num_args() -> Range<usize>

The possible range of function arguments

fn call(&self, input: &Input<'js>) -> Result<Value<'js>>

Call as JS function

fn post<'js_>(_ctx: Ctx<'js_>, _func: &Function<'js_>) -> Result<()>

Post-processing the function

impl<F> AsRef<RefCell<Option<F>>> for OnceFn<F>

fn as_ref(&self) -> &RefCell<Option<F>>

Performs the conversion.

impl<F> Deref for OnceFn<F>

type Target = RefCell<Option<F>>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<F> From<F> for OnceFn<F>

fn from(func: F) -> Self

Performs the conversion.