Struct tower::util::BoxLayer

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pub struct BoxLayer<In, T, U, E> { /* private fields */ }
Expand description

A boxed Layer trait object.

BoxLayer turns a layer into a trait object, allowing both the Layer itself and the output Service to be dynamic, while having consistent types.

This Layer produces BoxService instances erasing the type of the Service produced by the wrapped Layer.

§Example

BoxLayer can, for example, be useful to create layers dynamically that otherwise wouldn’t have the same types. In this example, we include a Timeout layer only if an environment variable is set. We can use BoxLayer to return a consistent type regardless of runtime configuration:

use std::time::Duration;
use tower::{Service, ServiceBuilder, BoxError, util::BoxLayer};

fn common_layer<S, T>() -> BoxLayer<S, T, S::Response, BoxError>
where
    S: Service<T> + Send + 'static,
    S::Future: Send + 'static,
    S::Error: Into<BoxError> + 'static,
{
    let builder = ServiceBuilder::new()
        .concurrency_limit(100);

    if std::env::var("SET_TIMEOUT").is_ok() {
        let layer = builder
            .timeout(Duration::from_secs(30))
            .into_inner();

        BoxLayer::new(layer)
    } else {
        let layer = builder
            .map_err(Into::into)
            .into_inner();

        BoxLayer::new(layer)
    }
}

Implementations§

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impl<In, T, U, E> BoxLayer<In, T, U, E>

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pub fn new<L>(inner_layer: L) -> Self
where L: Layer<In> + Send + Sync + 'static, L::Service: Service<T, Response = U, Error = E> + Send + 'static, <L::Service as Service<T>>::Future: Send + 'static,

Create a new BoxLayer.

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impl<In, T, U, E> Clone for BoxLayer<In, T, U, E>

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fn clone(&self) -> Self

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<In, T, U, E> Debug for BoxLayer<In, T, U, E>

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fn fmt(&self, fmt: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<In, T, U, E> Layer<In> for BoxLayer<In, T, U, E>

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type Service = BoxService<T, U, E>

The wrapped service
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fn layer(&self, inner: In) -> Self::Service

Wrap the given service with the middleware, returning a new service that has been decorated with the middleware.

Auto Trait Implementations§

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impl<In, T, U, E> Freeze for BoxLayer<In, T, U, E>

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impl<In, T, U, E> !RefUnwindSafe for BoxLayer<In, T, U, E>

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impl<In, T, U, E> Send for BoxLayer<In, T, U, E>

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impl<In, T, U, E> Sync for BoxLayer<In, T, U, E>

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impl<In, T, U, E> Unpin for BoxLayer<In, T, U, E>

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impl<In, T, U, E> !UnwindSafe for BoxLayer<In, T, U, E>

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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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,

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

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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

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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> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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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>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.