# [−][src]Struct std::future::FutureObj

    pub struct FutureObj<'a, T>(_);

🔬 This is a nightly-only experimental API. (`futures_api` #50547)

futures in libcore are unstable

A custom trait object for polling futures, roughly akin to `Box<dyn Future<Output = T> + Send + 'a>`.

This custom trait object was introduced for two reasons:

- Currently it is not possible to take `dyn Trait` by value and `Box<dyn Trait>` is not available in no_std contexts.
- The `Future` trait is currently not object safe: The `Future::poll` method makes uses the arbitrary self types feature and traits in which this feature is used are currently not object safe due to current compiler limitations. (See tracking issue for arbitrary self types for more information #44874)

## Methods

###

`impl<'a, T> FutureObj<'a, T>`

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####

`pub fn new<F>(f: F) -> FutureObj<'a, T> where F: Send + UnsafeFutureObj<'a, T>,`

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🔬 This is a nightly-only experimental API. (`futures_api` #50547)

futures in libcore are unstable

Create a `FutureObj` from a custom trait object representation.

## Trait Implementations

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`impl<'a, T> Debug for FutureObj<'a, T>`

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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

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`impl<'a, T> From<FutureObj<'a, T>> for LocalFutureObj<'a, T>`

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`fn from(f: FutureObj<'a, T>) -> LocalFutureObj<'a, T>`

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Performs the conversion.

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`impl<'a, T> Unpin for FutureObj<'a, T>`

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`impl<'a, T> Future for FutureObj<'a, T>`

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#### `type Output = T`

🔬 This is a nightly-only experimental API. (`futures_api` #50547)

futures in libcore are unstable

The result of the `Future`.

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`fn poll(self: PinMut<FutureObj<'a, T>>, cx: &mut Context) -> Poll<T>`

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🔬 This is a nightly-only experimental API. (`futures_api` #50547)

futures in libcore are unstable

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

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`impl<'a, T> Send for FutureObj<'a, T>`

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`impl<'a, F> From<PinBox<F>> for FutureObj<'a, ()> where F: 'a + Send + Future<Output = ()>,`

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`fn from(boxed: PinBox<F>) -> FutureObj<'a, ()>`

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Performs the conversion.

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`impl<'a, F> From<Box<F>> for FutureObj<'a, ()> where F: 'a + Send + Future<Output = ()>,`

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`fn from(boxed: Box<F>) -> FutureObj<'a, ()>`

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Performs the conversion.

## Auto Trait Implementations

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`impl<'a, T> !Sync for FutureObj<'a, T>`

## Blanket Implementations

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`impl<T, U> TryFrom for T where T: From<U>,`

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#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`

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🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

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`impl<T> From for T`

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`fn from(t: T) -> T`

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Performs the conversion.

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`impl<T, U> TryInto for T where U: TryFrom<T>,`

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#### `type Error = <U as TryFrom<T>>::Error`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`

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🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T, U> Into for T where U: From<T>,`

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`fn into(self) -> U`

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Performs the conversion.

###

`impl<T> Borrow for T where T: ?Sized,`

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####
ⓘImportant traits for &'a mut I

### Important traits for &'a mut I

`impl<'a, I> Iterator for &'a mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn borrow(&self) -> &T`

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Immutably borrows from an owned value. Read more

###

`impl<T> BorrowMut for T where T: ?Sized,`

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####
ⓘImportant traits for &'a mut I

### Important traits for &'a mut I

`impl<'a, I> Iterator for &'a mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn borrow_mut(&mut self) -> &mut T`

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Mutably borrows from an owned value. Read more

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`impl<T> Any for T where T: 'static + ?Sized,`

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`fn get_type_id(&self) -> TypeId`

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🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

Gets the `TypeId` of `self`. Read more

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