#Depot

Depot is used to store temporary data involved in a single request. Middleware can place processed temporary data into the Depot for use by subsequent handlers.

When a server receives a request from a client browser, it creates a Depot instance. This instance is destroyed after all middleware and Handler have finished processing the request.

For example, we can set current_user in authentication middleware, then read the current user information in subsequent middleware or handlers.

#Quick Understanding

Depot is used for storing and sharing data during request processing. It implements a type-safe data container supporting two primary usage patterns:

1. Key-Value Storage: Access values associated with string keys via insert/get methods
2. Type Injection: Store and retrieve values based on type through inject/obtain methods

As shown in examples, Depot is particularly useful for passing data between middleware and handlers. Middleware can set values (like user info, authentication status) in Depot, which subsequent handlers can access without recomputation or repeated queries. Depot's design ensures data consistency and accessibility throughout the request processing chain, making it a core tool for building complex web applications.

use salvo::prelude::*;

#[handler]
async fn set_user(depot: &mut Depot) {
    depot.insert("user", "client");
}
#[handler]
async fn hello(depot: &mut Depot) -> String {
    format!(
        "Hello {}",
        depot.get::<&str>("user").copied().unwrap_or_default()
    )
}

#[tokio::main]
async fn main() {
    tracing_subscriber::fmt().init();

    let router = Router::new().hoop(set_user).goal(hello);

    let acceptor = TcpListener::new("0.0.0.0:5800").bind().await;
    Server::new(acceptor).serve(router).await;
}

#Setting and Retrieving Data viainsert andget

As shown above, you can insert key-value pairs into Depot using insert. For such values, simply use get to retrieve them.

depot.insert("a", "b");
assert_eq!(depot.get::<&str>("a").copied().unwrap(), "b")

Returns None if the key doesn't exist or if the type doesn't match the stored value.

#Setting and Retrieving Data viainject andobtain

For cases where values don't need specific keys and only one instance per type exists, you can use inject to insert data and obtain to retrieve it. These methods don't require keys.

depot.inject(Config::new());
depot.obtain::<Config>();

#Overview of Depot Struct Methods