Module add_extension 

Middleware that clones a value into the incoming input extensions

Example

use std::{sync::Arc, convert::Infallible};

use rama_core::{extensions::{Extensions, ExtensionsRef}, Service, Layer, service::service_fn};
use rama_core::layer::add_extension::AddExtensionLayer;
use rama_core::error::BoxError;

// Shared state across all request handlers --- in this case, a pool of database connections.
struct State {
    pool: DatabaseConnectionPool,
}

// Request can be any type that implements [`ExtensionsRef`]
async fn handle(req: Extensions) -> Result<(), Infallible>
{
    // Grab the state from the request extensions.
    let state = req.extensions().get::<Arc<State>>().unwrap();

    Ok(())
}

// Construct the shared state.
let state = State {
    pool: DatabaseConnectionPool::new(),
};

let mut service = (
    // Share an `Arc<State>` with all requests.
    AddExtensionLayer::new(Arc::new(state)),
).into_layer(service_fn(handle));

// Call the service.
let response = service
    .serve(Extensions::new())
    .await?;

Note though that extensions are best not used for State that you expect to be there, but instead use extensions for optional behaviour to change. Static typed state is better embedded in service structs or as state for routers.

Structs

AddExtension

Middleware for adding some shareable value to incoming Context.

AddExtensionLayer

Layer for adding some shareable value to incoming Context.